Hydrocarboxylation of formaldehyde in the presence of a higher order carboxylic acid and heterogeneous catalyst

ABSTRACT

Disclosed is a process for the production and purification of glycolic acid or glycolic acid derivatives by the carbonylation of formaldehyde in the presence of a solid acid catalyst and a carboxylic acid. This invention discloses hydrocarboxylations and corresponding glycolic acid separations wherein the glycolic acid stream is readily removed from the carboxylic acid and the carboxylic acid is recycled.

FIELD OF THE INVENTION

This invention relates to a process for the production and purification of glycolic acid or glycolic acid derivatives by the carbonylation of formaldehyde in the presence of a solid acid catalyst and a carboxylic acid. This invention discloses hydrocarboxylations and corresponding glycolic acid separations wherein the glycolic acid stream is readily removed from the carboxylic acid and the carboxylic acid is recycled.

BACKGROUND OF THE INVENTION

Glycolic acid (also known as 2-hydroxyacetic acid or α-hydroxyacetic acid) can be used for many purposes including as a raw material to make ethylene glycol. Glycolic acid is prepared by the acid catalyzed reaction of carbon monoxide and formaldehyde in the presence of water, alcohols, and/or carboxylic acids. These processes often require high temperatures and pressures to proceed at practical rates. For example, glycolic acid typically is prepared by reacting formaldehyde with carbon monoxide and water in the presence of an acidic catalyst such as sulfuric acid under high temperature and pressure such as, for example, above 480 bar absolute (abbreviated herein as “bara”), and between 200 and 225° C. Alternatively, lower pressures may be employed in the presence of hydrogen fluoride as a catalyst and solvent. These processes, however, require expensive materials of construction and/or recovery and recycling schemes for hydrogen fluoride. Furthermore, readily available and less expensive formaldehyde starting material typically contains large concentrations of water that inhibit the rate of the carbonylation reaction and make purification of the glycolic acid product difficult. Separation of glycolic acid and the carboxylic acid is not feasible using distillation methods because the glycolic acid reacts with the carboxylic acid under typical process temperatures. Acetic acid is similar in its hydrophobicity to glycolic acid, making extraction methods unattractive for separating glycolic acid and acetic acid. Thus, there is a need for an economical process for making glycolic acid from an aqueous formaldehyde starting material that can be accomplished at moderate temperatures and pressures and allows for the ready separation of the glycolic acid from the crude hydrocarboxylation reactor product.

SUMMARY OF THE INVENTION

The present invention provides in one embodiment a process for the preparation of glycolic acid, comprising

-   -   (A) feeding carbon monoxide, aqueous formaldehyde, and a         carboxylic acid comprising 3-6 carbon atoms to a         hydrocarboxylation reaction zone comprising a solid acid         catalyst to produce an effluent comprising esters of glycolic         and carboxylic acids;     -   (B) hydrolyzing the effluent to produce a hydrolyzed mixture         comprising glycolic acid and the carboxylic acid;     -   (C) recovering the carboxylic acid from the hydrolyzed mixture         by extracting the hydrolyzed mixture with a hydrophobic solvent         selected from at least one of the group consisting of esters         having from 4 to 20 carbon atoms, ethers having from 4 to 20         carbon atoms, ketones having from 4 to 20 carbon atoms, and         hydrocarbons having from 6 to 20 carbon atoms to form an aqueous         raffinate phase comprising a major amount of the glycolic acid         contained in the hydrolyzed mixture and an organic extract phase         comprising a major amount of the carboxylic acid contained in         the hydrolyzed mixture; and     -   (D) separating the aqueous raffinate phase and the organic         extract phase.

The present invention provides in another embodiment a process for the preparation of glycolic acid, comprising

-   -   (A) feeding carbon monoxide, aqueous formaldehyde, and a         carboxylic acid selected from at least one of the group         consisting of propionic acid, n-butyric acid, i-butyric acid,         2-methyl butyric acid, n-valeric acid, and i-valeric acid to a         hydrocarboxylation reactor zone comprising a solid acid catalyst         to produce an effluent comprising esters of glycolic and         carboxylic acids;     -   (B) hydrolyzing the effluent to produce a hydrolyzed mixture         comprising glycolic acid and the carboxylic acid;     -   (C) recovering the carboxylic acid from the hydrolyzed mixture         by extracting the hydrolyzed mixture with a hydrophobic solvent         selected from at least one of the group consisting of n-propyl         acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate,         s-butyl acetate, methyl propionate, ethyl propionate, i-propyl         propionate, methyl tertiary-butyl ether, methyl i-butyl ketone,         methyl i-propyl ketone, methyl propyl ketone, and toluene to         form an aqueous raffinate phase comprising a major amount of the         glycolic acid contained in the hydrolyzed mixture and an organic         extract phase comprising a major amount of the carboxylic acid         contained in the hydrolyzed mixture; and     -   (D) separating the aqueous raffinate phase and the organic         extract phase.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of an embodiment of the present invention for hydrocarboxylation of an aqueous formaldehyde feed using propionic acid.

FIG. 2 is a schematic of an embodiment of the present invention for hydrocarboxylation of an aqueous formaldehyde feed using valeric acid.

DETAILED DESCRIPTION

The present invention provides in a first embodiment a process for the preparation of glycolic acid, comprising

-   -   (A) feeding carbon monoxide, aqueous formaldehyde, and a         carboxylic acid comprising 3-6 carbon atoms to a         hydrocarboxylation reaction zone comprising a solid acid         catalyst to produce an effluent comprising esters of glycolic         and carboxylic acids;     -   (B) hydrolyzing the effluent to produce a hydrolyzed mixture         comprising glycolic acid and the carboxylic acid;     -   (C) recovering the carboxylic acid from the hydrolyzed mixture         by extracting the hydrolyzed mixture with a hydrophobic solvent         selected from at least one of the group consisting of esters         having from 4 to 20 carbon atoms, ethers having from 4 to 20         carbon atoms, ketones having from 4 to 20 carbon atoms, and         hydrocarbons having from 6 to 20 carbon atoms to form an aqueous         raffinate phase comprising a major amount of the glycolic acid         contained in the hydrolyzed mixture and an organic extract phase         comprising a major amount of the carboxylic acid contained in         the hydrolyzed mixture; and     -   (D) separating the aqueous raffinate phase and the organic         extract phase.

Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Further, the ranges stated in this disclosure and the claims are intended to include the entire range specifically and not just the endpoint(s). For example, a range stated to be 0 to 10 is intended to disclose all whole numbers between 0 and 10 such as, for example 1, 2, 3, 4, etc., all fractional numbers between 0 and 10, for example 1.5, 2.3, 4.57, 6.1113, etc., and the endpoints 0 and 10. Also, a range associated with chemical substituent groups such as, for example, “C₁ to C₅ hydrocarbons”, is intended to specifically include and disclose C₁ and C₅ hydrocarbons as well as C₂, C₃, and C₄ hydrocarbons.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

It is to be understood that the mention of one or more process steps does not preclude the presence of additional process steps before or after the combined recited steps or intervening process steps between those steps expressly identified. Moreover, the lettering of process steps or ingredients is a convenient means for identifying discrete activities or ingredients and the recited lettering can be arranged in any sequence, unless otherwise indicated.

As used herein the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

The term “glycolic acid”, as used herein, refers to the chemical compound, glycolic acid, also known as 2-hydroxyacetic acid. The term “glycolic acid oligomers”, as used herein, refers to the reaction products of glycolic acid with itself, particularly the linear or cyclic esters formed by a reaction between the carboxyl group of one molecule and the alcohol group of another molecule. The “glycolic acid oligomers” include, but are not limited to, (2-hydroxyacetoxy)acetic acid (G2), 2-(2′-hydroxyacetoxy)acetoxyacetic acid (G3), and 2-(2′-(2″-hydroxyacetoxy)acetoxy)acetoxyacetic acid (G4). The term “esters of glycolic and carboxylic acids”, as used herein, refers to the esters produced by the reaction of a carboxylic acid with the hydroxyl end of glycolic acid and/or its oligomers.

The term “hydrocarboxylation reaction zone”, as used herein, refers to the part of the process wherein the carbon monoxide, aqueous formaldehyde, and carboxylic acid are fed, a solid acid catalyst is fed to or contained therein, and esters of glycolic and carboxylic acids are produced. The term “effluent”, as used herein, refers to the liquid stream exiting the hydrocarboxylation reaction zone comprising the “esters of glycolic and carboxylic acids”.

The term “hydrolyzing”, as used herein, refers to reacting with water. The term “hydrolyzed mixture”, as used herein, refers to the effluent from a hydrocarboxylation reaction zone after “hydrolyzing” it; the “hydrolyzed mixture” comprises glycolic acid and carboxylic acid that are the product of “hydrolyzing” the “esters of glycolic and carboxylic acids”.

The term “extracting”, as used herein, refers to separating a component from a feed into an immiscible liquid based upon relative differences in solubility. As used herein, the term “feed” is intended to have its commonly understood meaning in the liquid-liquid extraction art, which is the solution that contains the materials to be extracted or separated. The term “extraction solvent”, as used herein, is intended to be synonymous with the term “extractant” or “solvent” and is intended to mean the immiscible liquid that is used in the extraction process to extract materials or solutes from the feed. The term “extract” is the immiscible liquid left from the extraction solvent after it has been contacted with the feed. The term “raffinate” is intended to mean the liquid phase left from the feed after it has been contacted with the extraction solvent. The term “wash solvent” is understood to mean a liquid used to wash or enhance the purity of the raffinate or extract phase.

The term “hydrophobic solvent”, as used herein, refers to a solvent that will phase separate when mixed with water. The “hydrophobic solvent” is synonymous with the extractant solvent for the present invention. In the present invention, examples of hydrophobic solvents are “esters”, “ethers”, “ketones”, and “hydrocarbons” which are terms well known to those skilled in the art. In the present invention, the extraction produces an organic extract phase and an aqueous raffinate phase. The term a “major amount”, as used herein, for example “a major amount of the glycolic acid contained in the hydrolyzed mixture” refers to at least 50 weight percent of the glycolic acid contained in the hydrolyzed mixture. In a further example, when a raffinate phase comprises a major amount of the glycolic acid in the hydrolyzed mixture, the weight of the glycolic acid in the raffinate phase divided by the weight of the glycolic acid in the hydrolyzed mixture is at least 50 weight percent. The term a “minor amount”, as used herein, for example “a minor amount of glycolic acid in the hydrolyzed mixture” refers to less than 50 weight percent of the glycolic acid in the hydrolyzed mixture. The term “hydrophilic solvent”, as used herein, refers to a solvent that is miscible with water.

The term “molar ratio”, as used herein, refers to the moles of one component divided by the moles of another component. For example, if the molar ratio of carboxylic acid to formaldehyde is 2:1, then for every mole of formaldehyde, there are two moles of carboxylic acid. Note that the water in any aqueous formaldehyde feed is not considered in the molar ratio of carboxylic acid to formaldehyde.

The terms “reactions of ethylene glycol and glycolic acid”, and “reacting ethylene glycol and glycolic acid”, and “reacting ethylene glycol with an aqueous raffinate phase” which comprises glycolic acid, as used herein, refer to the many reactions that occur when ethylene glycol and glycolic acid are present at typical reaction conditions. The reactions include reactions between ethylene glycol and glycolic acid and reactions of glycolic acid with itself. Additionally, the reactions include reactions between ethylene glycol, glycolic acid, and glycolic acid oligomers or other reaction products such as 2-hydroxyethyl 2-hydroxyacetate. The term “glycolate ester oligomers”, as used herein, refers to the many reaction products of glycolate esters formed by “reacting ethylene glycol and glycolic acid”. Examples include, but are not limited to, 2-hydroxyethyl 2-hydroxyacetate, 1,2-ethanediyl bis(2-hydroxyacetate), 2′-[2″-(2′″-hydroxyacetoxy)acetoxy]ethyl 2-hydroxyacetate, 2′-(2″-[2′″-(2″″-hydroxyacetoxy)acetoxy]acetoxy)ethyl 2-hydroxyacetate, 2″-hydroxyethyl (2′-hydroxyacetoxy)acetate, 2′″-hydroxyethyl 2′-(2″-hydroxyacetoxy)acetoxyacetate, and 2′″-hydroxyethyl 2′-[2″-(2′″-hydroxyacetoxy)acetoxy]acetoxyacetate.

The aqueous formaldehyde used in the hydrocarboxylation reaction typically comprises 35 to 85 weight percent formaldehyde. Other examples of formaldehyde levels in the aqueous formaldehyde feed are 40 to 70 weight percent and 40 to 60 weight percent. These ranges are typical concentrations that can be achieved with conventional formaldehyde processes without further distillation. Conventional formaldehyde processes are described in “Formaldehyde”, Kirk-Othmer Encyclopedia, Vol. 11, 4^(th) Edition, 1994. For example, commercially available formaldehyde typically contains approximately 55 weight percent formaldehyde in water. Other forms of formaldehyde may be present in the aqueous formaldehyde feedstock including trioxane or paraformaldehyde and linear oligomers and polymers of formaldehyde, i.e., poly(oxymethylene) glycols and derivatives thereof, formed from the polymerization or oligomerization of formaldehyde in water or other solvents. The term “formaldehyde”, as used herein, is intended to include all the various forms of formaldehyde described above.

In the process of the present invention, the carboxylic acid serves as a solvent and promoter for the hydrocarboxylation reaction. The carboxylic acid will react in the hydrocarboxylation reaction zone to form a corresponding acyloxyacetic acid. For example, acetic acid can react to form acetoxyacetic acid, propionic acid can react to form 2-propionoxyacetic acid, and the like. The acyloxyacetic acids are hydrolyzed to produce glycolic acid and the carboxylic acid. The carboxylic acid is chosen to give the best improvement to the hydrocarboxylation reaction conversions and reaction selectivities while simultaneously providing easy separation between the glycolic acid and carboxylic acid. In one example, the carboxylic acid comprises 3 to 6 carbon atoms. In another example, the carboxylic acid comprises 3 to 5 carbon atoms. The carboxylic acid can be one or more of propionic acid, n-butyric acid, i-butyric acid, 2-methyl butyric acid, n-valeric acid, and i-valeric acid. In one example, the carboxylic acid comprises propionic acid. In another example, the carboxylic acid comprises n-valeric acid.

In the process of the present invention the molar ratio of carboxylic acid to formaldehyde (carboxylic acid:formaldehyde) fed to the hydrocarboxylation zone can vary over a considerable range. Examples include feeding at a carboxylic acid:formaldehyde ratio of from 0.2:1 to 10:1, or 0.2:1 to 6:1, or 0.2:1 to 4:1, or 0.2:1 to 2.5:1, or 0.2:1 to 2:1, or 0.5:1 to 10:1, or 0.5:1 to 6:1, or 0.5:1 to 4:1, or 0.5:1 to 2.5:1, or 0.5:1 to 2:1, or 0.7:1 to 10:1, or 0.7:1 to 0.7:6, or 0.7:1 to 0.7:4, or 0.7:1 to 0.7:2.5, or 0.7:1 to 2:1.

The hydrocarboxylation process can be carried out by feeding carbon monoxide to a reaction mixture comprising aqueous formaldehyde in the presence of a solid acid catalyst. The carbon monoxide typically is supplied to the reaction mixture in sufficient excess to insure an adequate supply thereof for absorption by the formaldehyde and to retard side reactions such as, for example, the decomposition of the formaldehyde to carbon monoxide and hydrogen or other products. The amount of carbon monoxide useful for the carbonylation reaction ranges from a molar ratio of 1:1 to 1, 000:1 or 1:1 to 100:1 or 1:1 to 20:1 or 1:1 to 20:1 or 2:1 to 20:1 or 2:1 to 10:1 of carbon monoxide to formaldehyde or formaldehyde equivalents.

The composition of the carbon monoxide stream required for hydrocarboxylation may comprise carbon monoxide, hydrogen, and carbon dioxide. For example, the carbon monoxide may be supplied in substantially pure form or as a mixture with other gases such as, for example, hydrogen, carbon dioxide, methane, nitrogen, noble gases (e.g., helium and argon), and the like. For example, the carbon monoxide need not be of high purity and may contain from 1% by volume to 99% by volume carbon monoxide. The remainder of the gas mixture may include such gases as, for example, nitrogen, hydrogen, water, carbon dioxide, noble gases, and paraffinic hydrocarbons having from one to four carbon atoms. In order to reduce compression costs, it is desirable for the carbon monoxide stream to comprise at least 95 mole % carbon monoxide, more preferably at least 99 mole %.

The carbon monoxide may be obtained from typical sources that are well known in the art. For example, the carbon monoxide may be provided by any of a number of methods known in the art including steam or carbon dioxide reforming of carbonaceous materials such as natural gas or petroleum derivatives; partial oxidation or gasification of carbonaceous materials, such as petroleum residuum, bituminous, sub bituminous, and anthracitic coals and cokes; lignite; oil shale; oil sands; peat; biomass; petroleum refining residues of cokes; and the like. For example, the carbon monoxide may be provided to the reaction mixture as a component of synthesis gas or “syngas”, comprising carbon dioxide, carbon monoxide, and hydrogen.

The hydrocarboxylation process can be conducted under continuous, semi-continuous, and batch modes of operation and may utilize a variety of reactor types. Examples of suitable reactor types include, but are not limited to, stirred tank, continuous stirred tank, trickle bed, tower, slurry, and tubular reactors. A typical temperature range for the hydrocarboxylation reaction is from 110 to 220° C. Other examples of the temperature range are from 110 to 210° C., 110 to 200° C., 110 to 190° C., 120 to 220° C., 120 to 210° C., 120 to 200° C., 140 to 220° C., 140 to 210° C., or 150 to 210° C. Examples of pressure ranges for the hydrocarboxylation reaction are 35 to 250 bar gauge, 35 to 200 bar gauge, and 60 to 200 bar gauge. In one example of the process, carbon monoxide, aqueous formaldehyde comprising 35 weight percent to 85 weight percent formaldehyde, based on the total weight of the aqueous formaldehyde, and carboxylic acid are fed at a molar ratio of carbon monoxide to formaldehyde ranging from 1:1 to 10:1, and the hydrocarboxylation reaction zone is operated at a pressure of from 35 bar gauge to 200 bar gauge and a temperature of from 120° C. to 220° C.

The hydrocarboxylation reactants may be introduced separately or in any sequence or combination to the hydrocarboxylation reaction zone. In addition, one or more reactants may be introduced at different locations in the reactor. For example, in a continuously operated process containing a catalyst bed in a reactor, the addition of water or formaldehyde may be staged throughout the reactor. In some cases, it may be desirable to recirculate a portion of the reaction media to the reactor to act as a liquid reaction media for the next synthesis. In order to reduce by-product formation, it is desirable to set the residence time in the hydrocarboxylation reaction zone to give an outlet formaldehyde concentration of 5 weight percent or less. In addition to glycolic acid, the hydrocarboxylation process typically produces glycolic acid oligomers, water, and unreacted formaldehyde. When carboxylic acids are present, the hydrocarboxylation process typically also produces esters of glycolic and carboxylic acids.

The advantages of using solid acid catalysts in the hydrocarboxylation reaction include being able to readily separate the reaction product and catalyst by mechanical means. The liquid phase reaction of carbon monoxide and formaldehyde is promoted by using certain solid phase, insoluble particulate catalyst materials. The term “insoluble” as used herein means that the catalyst is substantially insoluble in any combination of reactants or reaction products under reaction conditions present in the practice of hydrocarboxylation. The description of the catalyst as “particulate” refers to its size being such that it is separable from a liquid medium by simple means. Typical catalyst particle diameters are 2.0 to 0.001 millimeters.

In general, substances capable of forming Lewis or Brønsted type acids are useful catalysts. Examples of solid acids include strong acid cation exchange resins, solidified acids, clay minerals, zeolites, inorganic oxides and composite oxides. They are characterized in having their acid function available on a solid surface without releasing acidity into the liquid reaction medium. The acidity required of materials useful as catalysts in the practice of this invention may be measured as hydrogen ion exchange capacity. Although the catalysts or process of the present invention are not based on any theory of ion-exchange, it is useful to define the acidity criteria of acceptable solid catalysts as those which have hydrogen ion-exchange capacity of at least 0.1 milliequivalents per gram.

Strong acid type cation-exchange resins in hydrogen form are useful catalysts in the practice of hydrocarboxylation. Illustrative resins are those strong acid types having sulfonic acid functionality. The strong acid moiety may be pendant to a variety of polymeric backbones such as styrene-divinylbenzene or tetrafluoroethylene. The choice of polymeric backbone will depend on a variety of factors such as cost and temperature resistance. For instance, AMBERLYST resins produced by Rohm & Haas, Inc. are sulfonated styrene-divinylbenzene with increasing degrees of crosslinking corresponding to higher divinylbenzene content: AMBERLYST 15, 36 and 70 have maximum recommended operating temperatures of 120, 150 and 190° C., respectively. SMOPEX resins, offered by Johnson Matthey are sulfonic acid resins with a polyethylene backbone. SMOPEX 101 with 4%, 8% and 12% crosslinking have maximum operating temperatures of 160-190° C. NAFION resins offered by DuPont Inc. are sulfonated resins with fluorinated polymer backbones, providing very high acidity and chemical resistance. NAFION 50 has a maximum recommended operating temperature of 160° C.

Solid acids may also be composed of strongly acidic materials deposited on a robust support such as SAC-13 offered by BASF which contains 13% NAFION supported on silica. Likewise, Johnson Matthey offers 20% tungsten/silica which is a dicesium phosphotungstic acid (a heteropolyacid: Cs₂HPW₁₂O₄₀) supported on silica.

Examples of the clay minerals and zeolites include montmorillonite, kaolinite, bentonite, halloysite, smectite, illite, vermiculite, chlorite, sepiolite, attapulgite, palygorskite and mordenite. In particular, among these clay minerals and zeolites, preferred are those treated with an acid such as hydrogen fluoride, or those obtained by replacing a replaceable metal ion of these clay minerals and zeolites with a hydrogen ion such as H-type zeolite. Süd-Chemie offers K10 catalyst which is an example of an activated clay and has been demonstrated in this work.

In one example, the solid acid catalyst is selected from at least one of the group consisting of sulfonic acid resins, silica-aluminate, silica-alumino-phosphates, heteropolyacids, supported heteropolyacids, sulfuric acid treated metal oxides, and phosphoric acid treated metal oxides. Examples in addition to the specific commercially available catalysts above include the following. Examples of sulfonic acid resins include, but are not limited to, sulfonic acid resins of at least one of the group selected from polystyrene, polyethylene, fluorinated polymers, brominated polystyrene, chlorinated polystyrene, and fluorinated polystyrene. Examples of silica-aluminates include, but are not limited to, Zeolites such as pentasils, faujasites, chabazites, mordenites, offretites, stilbites, clinoptolites, natrolites, and the like. Examples of silica-alumino-phosphates include, but are not limited to, SAPO-5 and SAPO-34. The heteropolyacid comprises metal addenda atoms, such as tungsten, molybdenum, or vanadium, linked by oxygen atoms form a hetero-atom-centered cluster bonded via oxygen atoms. The hetero-atom is selected generally from the p-block of the periodic table, such as silicon, phosphorus, or arsenic. Examples of heteropolyacid structure are Keggin, H_(n)XM₁₂O₄₀, and Dawson, H_(n)X₂M₁₈O₆₂, type clusters, such as, but not limited to H₄X^(n+)M₁₂O₄₀, wherein X=Si, Ge and M=Mo, W; H₃X^(n+)M₁₂O₄₀, wherein X═P, As and M=Mo, W; and H₆X₂M₁₈O₆₂, wherein X═P, As and M=Mo, W. Examples of supported heteropolyacids include, but are not limited to, H₃PMo₁₂O₄₀ on silica, H₃PW₁₂O₄₀ on silica, and H₄SiW₁₂O₄₀ on silica. Examples of sulfuric acid treated metal oxides include, but are not limited to, SiO₂ treated with sulfuric acid, TiO₂ treated with sulfuric acid, ZrO₂ treated with sulfuric acid, and TiO₂/MoO₂ mixed metal oxide treated with sulfuric acid. Examples of phosphoric acid treated metal oxides include, but are not limited to, niobium oxide treated with phosphoric acid and tungsten oxide treated with phosphoric acid.

In general, the rate of reaction increases with increasing catalyst concentration. Because solid catalysts are easily separated from the reaction mixture, they can be used at higher levels to achieve shorter reaction times, lower temperatures, or lower pressures. Although the catalyst may be present in amounts as low as to provide a minimum of 0.01 mole of hydrogen ion per mole of formaldehyde, greater proportions of catalyst, approaching or exceeding one mole of hydrogen ion per mole of formaldehyde reactant, can be used to achieve higher reaction rates. In one embodiment of the process of the invention, for example, the process can be operated as a continuous process in which the maximum allowable catalyst concentration is limited only by the weight of catalyst which may be packed into the volume of the hydrocarboxylation reaction zone while preserving effective contact of reactants and practical flow rates.

In the process of the present invention, an effluent comprising esters of glycolic and carboxylic acids is produced in the hydrocarboxylation reaction zone. The esters of glycolic and carboxylic acids are produced by the reaction of a carboxylic acid with the hydroxyl end of glycolic acid and/or its oligomers. In one example, the esters of glycolic and carboxylic acid are selected from the esters of glycolic and propionic acid, the esters of glycolic and n-butyric acid, the esters of glycolic and i-butyric acid, the esters of glycolic and 2-methyl butyric acid, the esters of glycolic and n-valeric acid, the esters of glycolic and i-valeric acid, or mixtures thereof. In another example, the esters of glycolic and carboxylic acids comprise 2-propionoxyacetic acid and/or (2′-(propionyloxy)acetoxyacetic acid. In another example, the esters of glycolic and carboxylic acids comprise 2-valeryloxyacetic acid, (2′-valeryloxy)acetoxyacetic acid, and/or [2′-(2″-valeryloxy)acetoxy]acetoxyacetic acid.

The effluent from the hydrocarboxylation reaction zone may be hydrolyzed by means known to one skilled in the art. Typically, water will be added to the effluent in an excess of the amount needed to react with the esters of glycolic and carboxylic acids to produce a hydrolyzed mixture comprising glycolic acid and the carboxylic acid. For example, when propionic acid is the carboxylic acid, the effluent comprises esters of glycolic of carboxylic acids which include, but are not limited to, 2-propionoxyacetic acid and (2′-(propionyloxy)acetoxyacetic acid. The glycolic acid oligomers react with water to form glycolic acid and the 2-propionoxyacetic acid and (2′-(propionyloxy)acetoxyacetic acid react with water to form propionic acid and glycolic acid. In one example the hydrolyzed mixture comprises glycolic acid and at least one carboxylic acid selected from propionic acid, n-butyric acid, i-butyric acid, 2-methyl butyric acid, n-valeric acid, and i-valeric acid. In another example, the hydrolyzed mixture comprises glycolic acid and propionic acid. In another example, the hydrolyzed mixture comprises glycolic acid and valeric acid.

The composition of the hydrolyzed mixture can vary. While increase in the amount of water may improve hydrolysis rates, the additional water must be separated from the glycolic acid. In one example, the molar ratio of water to glycolic acid in the resulting hydrolyzed mixture (water:glycolic acid) is from 1:1 to 15:1. Other examples of water:glycolic acid are from 1:1 to 8:1, or 1:1 to 6:1, or 1.5:1 to 15:1, or 1.5:1 to 8:1, or 1.5:1 to 6:1 or 2:1 to 15:1, or 2:1 to 8:1, or 2:1 to 6:1.

In the process of the present invention, the carboxylic acid is recovered by extracting the hydrolyzed mixture with a hydrophobic solvent with the glycolic acid partitioning to the raffinate. The hydrophobic solvent can be selected from esters having from 4 to 20 carbon atoms, ethers having from 4 to 20 carbon atoms, and hydrocarbons having from 6 to 20 carbon atoms. In one aspect of the invention, the hydrophobic solvent comprises ethyl acetate, n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate, s-butyl acetate, methyl benzoate, i-butyl isobutyrate, 2-ethylhexyl acetate, cyclohexyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, i-propyl propionate, i-butyl propionate, n-butyl propionate, s-butyl propionate, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ethers, methyl tertiary-butyl ether, methyl tertiary-amyl ether, methyl ethyl ketone, methyl i-butyl ketone, methyl i-propyl ketone, methyl propyl ketone, dibutyl ketone, diisobutyl ketone, isophorone, 3,3,5-trimethylcyclohexanone, cyclohexanone, 2-heptanone, methyl-iso-amyl ketone, diethyl ketone, 5-ethyl 2-nonanone, diamyl ketone, diisoamyl ketone, heptane, hexane, toluene, or mixtures thereof. In another aspect of the invention, the hydrophobic solvent comprises n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate, s-butyl acetate, methyl propionate, ethyl propionate, i-propyl propionate, methyl tertiary-butyl ether, methyl i-butyl ketone, methyl i-propyl ketone, methyl propyl ketone, toluene, or mixtures thereof. In yet another aspect of the invention, the hydrophobic solvent comprises n-propyl acetate, i-propyl acetate, methyl propionate, ethyl propionate, i-propyl propionate, methyl tertiary-butyl ether, methyl i-butyl ketone, or mixtures thereof.

The process of the present invention forms an aqueous raffinate phase comprising a major amount of glycolic acid and a minor amount of carboxylic acid contained in the hydrolyzed mixture. In an aspect of the invention, greater than 80 weight percent of the glycolic acid in the hydrolyzed mixture is recovered in the raffinate phase. In another aspect, greater than 90 weight percent, greater than 95 weight percent, greater than 98 weight percent, greater than 99 weight percent, or greater than 99.5 weight percent of the glycolic acid in the hydrolyzed mixture is recovered in the aqueous raffinate phase.

The process of the present invention forms an organic extract phase comprising a major amount of the carboxylic acid and a minor amount of the glycolic acid. In an aspect of the invention greater than 90 weight percent of the carboxylic acid in the hydrolyzed mixture is recovered in the organic extract phase. In another aspect, greater than 95 weight percent, greater than 98 weight percent, or greater than 99 weight percent, or greater than 99.5 weight percent, or greater than 99.9 weight percent of the carboxylic acid in the hydrolyzed mixture is recovered in the organic extract phase.

Extracting the hydrolyzed mixture can be carried out by any means known in the art to intimately contact two immiscible liquid phases and to separate the resulting phases after the extraction procedure. For example, the extraction can be carried out using columns, centrifuges, mixer-settlers, and miscellaneous devices. Some representative examples of extractors include unagitated columns (e.g., spray, baffle tray and packed, perforated plate), agitated columns (e.g., pulsed, rotary agitated, and reciprocating plate), mixer-settlers (e.g., pump-settler, static mixer-settler, and agitated mixer-settler), centrifugal extractors (e.g., those produced by Robatel, Luwesta, deLaval, Dorr Oliver, Bird, CINC, and Podbielniak), and other miscellaneous extractors (e.g., emulsion phase contactor, electrically enhanced extractors, and membrane extractors). A description of these devices can be found in the “Handbook of Solvent Extraction”, Krieger Publishing Company, Malabar, Fla., 1991, pp. 275-501. The various types of extractors may be used alone or in any combination.

The extraction may be conducted in one or more stages. The number of extraction stages can be selected in consideration of capital costs, achieving high extraction efficiency, ease of operability, and the stability of the hydrolyzed mixture and extraction solvents to the extraction conditions. The extraction also can be conducted in a batch or continuous mode of operation. In a continuous mode, the extraction may be carried out in a co-current, a counter-current manner, or as a fractional extraction in which multiple solvents and/or solvent feed points are used to help facilitate the separation. The extraction process also can be conducted in a plurality of separation zones that can be in series or in parallel.

The extraction typically can be carried out at a temperature of 10 to 120° C. For example, the extraction can be conducted at a temperature of 30 to 80° C. The desired temperature range may be constrained further by the boiling point of the extractant components or water. Generally, it is undesirable to operate the extraction under conditions where the extractant boils. In one aspect, the extractor can be operated to establish a temperature gradient across the extractor in order to improve the mass transfer kinetics or decantation rates. In another aspect, the extractor may be operated under sufficient pressure to prevent boiling.

In an aspect of the invention, the hydrolyzed mixture is extracted in a continuous counter-current extractor. The hydrophobic solvent is fed to the extractor at a location lower than the feed location of the hydrolyzed mixture. The hydrophobic solvent moves up the counter-current extractor to form an organic extract phase exiting the top of the extractor and comprising a major amount of the carboxylic acid and a minor amount of the glycolic acid contained in the hydrolyzed mixture. The hydrolyzed mixture moves down the counter-current extractor to form an aqueous raffinate phase exiting the bottom of the extractor and comprising a major amount of the glycolic acid and a minor amount of the carboxylic acid contained in the hydrolyzed mixture. In an aspect of the invention the feed ratio of the hydrophobic solvent to the hydrolyzed mixture on a weight basis ranges from 0.1:1 to 20:1, or 0.1:1 to 10:1, or 0.1:1 to 5:1, or 0.1:1 to 4:1, or 0.5:1 to 20:1, or 0.5:1 to 10:1, or 0.5:1 to 5:1, or 0.5:1 to 4:1, or 1:1 to 10:1, or 1:1 to 5:1, or 1:1 to 4:1.

The hydrolyzed mixture and hydrophobic solvent can be contacted by fractional extraction methods such as, for example, by fractional counter-current extraction. As used herein, the term “fractional counter-current extraction” is intended to include, but is not limited to, a method for separating a feed stream, e.g., hydrolyzed mixture, containing two or more substances by charging the feed stream to a counter-current extraction process between the points where two immiscible solvents are charged to the extraction process. The two immiscible solvents should be immiscible over the entire temperature range of the extraction process. This method is sometimes referred to as “double solvent extraction.” Fractional counter-current extraction can involve the use of a cascade of stages, extracting solvents and solution to be extracted entering at opposite ends of the cascade with the feed phase and hydrophobic extractant phase flowing counter-currently. Some example fractional counter-current extraction configurations may be found in Treybal, Liquid Extraction, 2nd Edition, McGraw-Hill Book Company, New York. 1963, pp. 275-276.

In an aspect of the invention, the hydrolyzed mixture is extracted in a continuous fractional counter-current extractor. The hydrophobic solvent is fed to the extractor at a location lower than the feed location of the hydrolyzed mixture. A hydrophilic solvent is fed to the extractor at a location higher than the hydrolyzed mixture. In an aspect of the invention the feed ratio of the hydrophobic solvent to the hydrolyzed mixture on a weight basis ranges from 0.5:1 to 20:1, or 1:1 to 10:1, or 1:1 to 5:1 and the feed ratio of the hydrophilic solvent to the hydrolyzed mixture on a weight basis ranges from 0.05:1 to 2:1, or 0.1:1 to 1.5:1, or 0.1:1 to 0.8:1. In one example, the hydrophilic solvent comprises water. In another example, the hydrophilic solvent comprises water and ethylene glycol. In another example, the hydrophilic solvent comprises 50 weight percent to 100 weight percent water and 0 weight percent to 50 weight percent ethylene glycol, each on a total hydrophilic solvent weight basis.

In the process of the present invention, the extracting of the hydrolyzed mixture results in an aqueous raffinate phase comprising a major amount of the glycolic acid and a minor amount of the carboxylic acid contained in the hydrolyzed mixture and an organic extract phase comprising a major amount of the carboxylic acid and a minor amount of the glycolic acid contained in the hydrolyzed mixture. The raffinate phase and the extract phase may be separated by any phase separation technology known in the art. The phase separation techniques can be accomplished in the extractor or in a separate liquid-liquid separation device. Suitable liquid-liquid separation devices include, but are not limited to, coalescers, cyclones and centrifuges. Typical equipment that can be used for liquid-liquid phase separation devices are described in the Handbook of Separation process Technology, ISBN 0-471-89558-X, John Wiley & Sons, Inc., 1987.

One aspect of our process includes (E) separating the organic extract phase into the hydrophobic solvent and the carboxylic acid, recycling the hydrophobic solvent to step (C), and recycling the carboxylic acid to step (A). The hydrophobic solvent and carboxylic acid can be separated by any means known to one skilled in the art. Examples include by distillation and extraction. In one example, the hydrophobic solvent has a lower boiling point than the carboxylic acid and the two components are separated via distillation. The hydrophobic solvent is recovered as the distillate product and recycled for extracting in step (C) and the carboxylic acid is the bottoms product and recycled to the hydrocarboxylation reaction zone in step (A). In another example, the hydrophobic solvent has a higher boiling point than the carboxylic acid and the two components are separated via distillation. The hydrophobic solvent is recovered as the bottoms product and recycled for extracting in step (C) and the carboxylic acid is the distillate product and recycled to the hydrocarboxylation reaction zone in step (A).

One aspect of our process further includes (F) reacting a first ethylene glycol with the aqueous raffinate phase while simultaneously removing water to produce an esterification effluent comprising glycolate ester oligomers and glycolic acid oligomers and an overhead stream comprising water; and (G) reacting hydrogen with the esterification effluent to produce a second ethylene glycol, separating the second ethylene glycol into a product ethylene glycol and the first ethylene glycol, and recycling the first ethylene glycol to step (F). The reaction between the first ethylene glycol and the glycolic acid of the aqueous raffinate phase and simultaneous removal of water can be conducted under standard esterification conditions known to persons skilled in the art. Part of the water in the aqueous raffinate phase can be removed prior to esterification. For example, the esterification can be achieved by adding hot ethylene glycol to the aqueous raffinate phase and removing water formed during esterification until sufficient water is removed and an esterification effluent comprising glycolate ester oligomers and glycolic acid oligomers is formed. Typically excess ethylene glycol is used to ensure complete esterification. Examples of mole ratios of ethylene glycol to glycolic acid vary from 0.25:1 to 10:1 of 0.25:1 to 6:1 or 0.25 to 3:1 or 0.5:1 to 10:1 or 0.5:1 to 6:1 or 0.5:1 to 3:1 or 1:1 to 10:1 or 1:1 to 6:1 or 1:1 to 3:1 or 1.5:1 to 10:1 or 1.5:1 to 6:1 or 1.5:1 to 3:1 or 2:1 to 10:10 or 2:1 to 6:1. Representative conditions for esterification include at a temperature of from 150 to 250° C., preferably from 170 to 220° C., and a pressure of from 1 bara to 8 bara, preferably from 1 bara to 5 bara.

The esterification effluent can be hydrogenated to produce ethylene glycol by contacting the glycolate ester oligomers and glycolic acid oligomers with hydrogen in the presence of a suitable hydrogenation catalyst. The hydrogenation reaction can be conducted in the liquid or the gas phase using known processes. Typically, glycolate ester oligomers and glycolic acid oligomers are contacted with hydrogen under pressure in the presence of a catalyst effective for hydrogenation at temperatures from 150 to 300° C. Additional examples of temperatures ranges are from 200 to 250° C. Examples of typical pressure ranges are from 35 bara to 350 bara and 70 bara to 140 bara. Considerable latitude in the temperature and pressure of hydrogenation is possible depending upon the use and choice of hydrogenation catalyst and whether the process is conducted in the liquid or gas phase.

The hydrogenation catalyst may comprise any metal or combination of metals effective for the hydrogenation of esters to alcohols. Typical hydrogenation catalysts include, but are not limited to, at least one metal selected from Groups 8, 9, 10 of the Periodic Table of the Elements (1984 Revision by IUPAC), and copper. In addition, the hydrogenation catalyst may comprise at least one additional metal promoter selected from chromium, magnesium, barium, sodium, nickel, silver, lithium, potassium, cesium, zinc, cobalt, and gold. The term “metal”, as used herein in the context of hydrogenation catalysts, is understood to include metals in their elemental form and compounds thereof such as, for example, metal oxides, salts, and complexes with organic ligands. For example, the hydrogenation catalyst can comprise a Raney nickel or a metal oxide. Typical metal oxide catalysts include, for example, copper chromite, copper oxide, or copper oxide in combination with the oxide of magnesium, barium, sodium, nickel, silver, lithium, potassium, cesium, zinc, cobalt and the like or mixtures thereof. In another example, the hydrogenation catalyst can comprise cobalt metal in combination with zinc and copper oxides.

The esterification effluent may be purified prior to hydrogenation or may proceed directly to the hydrogenation reaction. The hydrogenation reaction produces a second ethylene glycol. The second ethylene glycol may or may not be further purified before separation into a product ethylene glycol and a first ethylene glycol which is recycled to the esterification step (F).

The present invention provides in a second embodiment a process for the preparation of glycolic acid, comprising

-   -   (A) feeding carbon monoxide, aqueous formaldehyde, and a         carboxylic acid selected from at least one of the group         consisting of propionic acid, n-butyric acid, i-butyric acid,         2-methyl butyric acid, n-valeric acid, and i-valeric acid to a         hydrocarboxylation reactor zone comprising a solid acid catalyst         to produce an effluent comprising esters of glycolic and         carboxylic acids;     -   (B) hydrolyzing the effluent to produce a hydrolyzed mixture         comprising glycolic acid and the carboxylic acid;     -   (C) recovering the carboxylic acid from the hydrolyzed mixture         by extracting the hydrolyzed mixture with a hydrophobic solvent         selected from at least one of the group consisting of n-propyl         acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate,         s-butyl acetate, methyl propionate, ethyl propionate, i-propyl         propionate, methyl tertiary-butyl ether, methyl i-butyl ketone,         methyl i-propyl ketone, methyl propyl ketone, and toluene to         form an aqueous raffinate phase comprising a major amount of the         glycolic acid contained in the hydrolyzed mixture and an organic         extract phase comprising a major amount of the carboxylic acid         contained in the hydrolyzed mixture; and     -   (D) separating the aqueous raffinate phase and the organic         extract phase.

The examples of the first embodiment regarding aqueous formaldehyde, carboxylic acid, molar ratio of carboxylic acid to formaldehyde, carbon monoxide, hydrocarboxylation reaction zone process conditions, solid acid catalysts, esters of glycolic and carboxylic acids, hydrolyzing and hydrolyzed mixture composition, extraction, hydrophobic solvent and hydrophilic solvent, as well as feed ratios of each solvent to the hydrolyzed mixture on a weight basis, separation of the organic extract and aqueous raffinate, separation and recycle of the carboxylic acid and hydrophobic solvent, esterification of the glycolic acid and hydrogenation of the glycolate ester oligomers and glycolic acid oligomers to produce ethylene glycol apply to the second embodiment.

For example, the process of the invention includes an aspect wherein the feeding of the carboxylic acid and aqueous formaldehyde in step (A) occurs at a molar ratio of carboxylic acid:formaldehyde of 0.5:1 to 4:1 or 0.5:1 to 2.5:1. In another example, the hydrolyzed mixture comprises the molar ratio water:glycolic acid of from 1:1 to 8:1 or 1:1 to 6:1. In another example the hydrophobic solvent is selected from at least one of the group consisting of n-propyl acetate, i-propyl acetate, methyl propionate, ethyl propionate, i-propyl propionate, methyl tertiary-butyl ether, and methyl i-butyl ketone. In another example, the carboxylic acid comprises propionic acid.

In another example, greater than 90 weight percent of the carboxylic acid is recovered in the organic extract phase and greater than 90 weight percent of the glycolic acid is recovered in the aqueous raffinate phase. In another example, the extracting of step (C) occurs in a continuous counter-current extractor, wherein the aqueous raffinate phase exits the bottom of the extractor and the organic extract phase exits the top of the extractor, the hydrophobic solvent is fed to the extractor below the hydrolyzed mixture, and the feed ratio of the hydrophobic solvent to the hydrolyzed mixture ranges from 0.5:1 to 4:1 on a weight basis. Additionally, a hydrophilic solvent can be fed to the extractor above the hydrolyzed mixture, wherein the feed ratio of the hydrophilic solvent to the hydrolyzed mixture ranges from 0.01:1 to 5:1 on a weight basis, and the feed ratio of the hydrophobic solvent to the hydrolyzed mixture ranges from 0.5:1 to 4:1 on a weight basis.

In another example of the process of the present invention, the aqueous formaldehyde comprises 35 weight percent to 85 weight percent formaldehyde, based on the total weight of the aqueous formaldehyde, the molar ratio of carbon monoxide to formaldehyde ranges from 1:1 to 10:1, and the hydrocarboxylation reaction zone is operated at a pressure of from 35 bar gauge to 200 bar gauge and a temperature of from 120° C. to 220° C.

In yet another example, the above process further comprises (E) separating the organic extract phase into the hydrophobic solvent and the carboxylic acid, recycling the hydrophobic solvent to step (C), and recycling the carboxylic acid to step (A); (F) reacting a first ethylene glycol with the aqueous raffinate phase while simultaneously removing water to produce an esterification effluent comprising glycolate ester oligomers and glycolic acid oligomers and an overhead stream comprising water; and (G) reacting hydrogen with the esterification effluent to produce a second ethylene glycol, separating the second ethylene glycol into a product ethylene glycol and the first ethylene glycol, recycling the first ethylene glycol to step (F).

The present invention provides in a third embodiment a process for the preparation of glycolic acid, comprising

-   -   (A) feeding carbon monoxide, aqueous formaldehyde, and         carboxylic acid selected from at least one of the group         consisting of 2-methyl butyric acid, n-valeric acid, and         i-valeric acid to a hydrocarboxylation reactor zone comprising a         solid acid catalyst to produce an effluent comprising esters of         glycolic and carboxylic acids;     -   (B) hydrolyzing the effluent to produce a hydrolyzed mixture         comprising glycolic acid and the carboxylic acid;     -   (C) separating the hydrolyzed mixture into a aqueous phase         comprising glycolic acid and an organic phase comprising the         carboxylic acid and recycling the carboxylic acid to step (A).

The examples of the first embodiment regarding aqueous formaldehyde, carboxylic acid, molar ratio of carboxylic acid to formaldehyde, carbon monoxide, hydrocarboxylation reaction zone process conditions, solid acid catalysts, esters of glycolic and carboxylic acids, hydrolyzing and hydrolyzed mixture composition, esterification of the glycolic acid and hydrogenation of the glycolate ester oligomers and glycolic acid oligomers to produce ethylene glycol apply to the third embodiment. The aqueous phase and the organic phase may be separated by any phase separation technology known in the art. Suitable liquid-liquid separation devices for the separation include, but are not limited to, coalescers, cyclones and centrifuges.

In an example, the third embodiment further comprising adding a hydrophobic solvent prior to step (C) and separating the hydrophobic solvent from the carboxylic acid prior to recycling the carboxylic acid to step (A). The hydrophobic solvent can be selected from ethers having from 4 to 20 carbon atoms and hydrocarbons having from 6 to 20 carbon atoms. In one aspect of the invention, the hydrophobic solvent comprises diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ethers, methyl tertiary-butyl ether, methyl tertiary-amyl ether, heptane, hexane, toluene, or mixtures thereof. In another aspect of the invention, the hydrophobic solvent comprises n-methyl tertiary-butyl ether, toluene, or mixtures thereof.

FIGS. 1 and 2 present two, non-limiting embodiments or the instant invention described herein in detail. In a first embodiment of the invention as laid out in FIG. 1, Carbon Monoxide Stream 1, Aqueous Formaldehyde Stream 2, and Propionic Acid Stream 3 are fed to Hydrocarboxylation Reactor 50 which comprises a fixed bed, solid catalyst (not shown). The Effluent Stream 4 comprises the esters of glycolic and propionic acid including 2-propionoxyacetic acid and (2′-(propionyloxy)acetoxyacetic acid. Effluent Stream 4 and Water Stream 8 are fed to Hydrolyzer 55. Hydrolyzer 55 is operated at sufficient temperature, pressure, and residence time to produce Hydrolyzed Mixture Stream 9 comprising glycolic acid, propionic acid, and water. Hydrolyzed Mixture Stream 9 is extracted with Hydrophobic Solvent Stream 11, such as methyl tertiary-butyl ether, in Extractor 60, to produce Organic Extract Stream 10 and Aqueous Raffinate Stream 12. Organic Extract Stream 10 can be separated into Propionic Stream 3 and Hydrophobic Solvent Stream 11 in Separator 70. Separator 70 can be, for example a distillation column. Propionic Acid Stream 3 is recycled to Hydrocarboxylation Reactor 50 and Hydrophobic Solvent Stream 11 is recycled to Extractor 60.

Use of a hydrophobic solvent for extraction of the carboxylic acid from the hydrolyzed mixture is necessary if the carboxylic acid and aqueous glycolic acid does not phase separate and may be helpful to improve the separation even if not required to form two phases. In a second embodiment of the invention as set forth in FIG. 2, Carbon Monoxide Stream 1, Aqueous Formaldehyde Stream 2, and Valeric Acid Stream 3 are fed to Hydrocarboxylation Reactor 50 which comprises a fixed bed, solid catalyst (not shown). The Effluent Stream 4 comprises the esters of glycolic and valeric acid including 2-valeryloxyacetic acid. Effluent Stream 4 and Water Stream 8 are fed to Hydrolyzer 55. Hydrolyzer 55 is operated at sufficient temperature, pressure, and residence time to produce Hydrolyzed Mixture Stream 9 comprising glycolic acid, valeric acid, and water. Hydrolyzed Mixture Stream 9 is separated into two phases in Decanter 65. The organic phase is recycled to Hydrocarboxylation Reactor 50 as Valeric Acid Stream 3. Aqueous Glycolic Acid Stream 12 exits Decanter 65 and is fed, along with First Ethylene Glycol Stream 13 to Esterification Unit 80. Water Stream 14 and Glycolate Ester Oligomer Stream 15 exit Esterification Unit 80. Glycolate Ester Oligomer Stream 15 is hydrogenated using Hydrogen Stream 16 in Hydrogenation Unit 90. Hydrogenation Unit 90 produces Second Ethylene Glycol Stream 17 which can be split into Ethylene Glycol Product Stream 18 and First Ethylene Glycol Stream 13 which is recycled to Esterification Unit 80.

The invention can be further illustrated by the following examples of preferred embodiments thereof, although it will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention.

EXAMPLES

The compounds and abbreviations given in Table 1 are used throughout the Examples section. Structures for each compound are also given.

TABLE 1 Compound Names, Structures, and Abbreviation Name Structure Code Glycolic Acid

G1 (2- Hydroxyacetoxy)- acetic Acid

G2 2-(2′- Hydroxyacetoxy)- acetoxyacetic Acid

G3 2-(2′-(2″- Hydroxyacetoxy)- acetoxy)acetoxyacetic Acid

G4 Acetic Acid

A2 Acetoxyacetic acid

A2GH Propionic Acid

A3 2-Propionoxyacetic Acid

A3GH 2-Propionoxyacetic Acid Oligomer

A3GnH n = 2-4 Valeric Acid

A5 2-Valeryloxyacetic Acid

A5GH (2′-Valeryloxy)- acetoxyacetic Acid

A5G2H [2′-(2″- Valeryloxy)acetoxy]- acetoxyacetic Acid

A5G3H Formaldehyde

F0 Methylene Glycol

F1 Polymethylene glycol

Fn n = 2-10 Formic Acid

A1 Diglycolic Acid

DG 2-Methoxyacetic Acid

MGH Methyl Glycolate

MG Methylene Diacetate

MDA Methylene Dipropionate

MDP

Materials—Acetic and propionic acids (99.5%), nonafluorobutanesulfonic acid and AMBERLYST 36 ion exchange resin were purchased from Aldrich Chemical Company. AMBERLYST resin, manufactured by Rohm & Hass Chemical Company, is crosslinked polystyrene beads that have been sulfonated. AMBERLYST 36D is <1.65% wet with 5.4 meq/g acid capacity and a recommended maximum operating temperature of 150° C. Sulfuric acid was purchased from J. T. Baker, trifluoromethanesulfonic acid (also known as triflic acid) and bis(trifluoromethylsulfonyl)amide were purchased from SynQuest Labs, Inc., tetrafluoroethanesulfonic acid was purchased from DuPont Chemical Company. Paraformaldehyde (90% min) was purchased from Kodak. Solid acid catalysts were received from suppliers as detailed below. All chemicals were used as received except as noted below.

Yield—

Ultimately, the hydrocarboxylation process is used to produce glycolic acid. The crude product from a hydrocarboxylation reaction, which takes place in carboxylic acid, comprises the esters of glycolic and carboxylic acids. For example, when the carboxylic acid is propionic acid, the crude product comprises methyl glycolate (MG), glycolic acid (G1) and its oligomers (Gn, n=2-5) and 2-propionoxyacetic acid (A3 GH) and its oligomers (A3GnH, n=2-4). When a GC method was used, the yield of desired products was calculated based upon the total moles of glycolic acid moiety. The term “glycolic acid moiety,” as used herein, refers to the O—CH₂—CO₂ segment of a molecule, for example, the segment in glycolic acid, a glycolic acid oligomer, or an ester of glycolic and carboxylic acids. The glycolic acid moieties divided by the moles of formaldehyde fed gives the yield. When an LC method was used, all of the glycolic acid moieties are converted to glycolic acid by the sample preparation. The yield was calculated simply as the moles of glycolic acid divided by the moles of formaldehyde fed.

Selectivity—

Selectivities to glycolic acid were calculated as the total moles of desired product for GC method as given above or the total moles of glycolic acid for the HPLC method divided by moles of all products formed from formaldehyde such as formic acid, methyl glycolate, diglycolic acid, and others.

Gas Chromatography (GC) Method 1. Samples were analyzed using a Hewlett-Packard HP-5890 chromatograph equipped with split injectors and FIDs. The injector and detector port temperatures were 250° C. and 300° C., respectively. A DB-5 [(5% phenyl)-methylpolysiloxane] capillary column was employed. Hydrogen was used as the carrier gas with a column head pressure of 9 psig and a column flow of 1.6 ml/minute, which gave a carrier gas linear velocity of 43 cm/second. 0.5-μl of the prepared sample solution was injected with a split ratio of 40:1. The column temperature was programmed as follows: the initial oven temperature was set at 80° C. and was held for 3 minutes, the oven was then ramped up to 280° C. at a rate of 10° C./minute and was held at 280 for 7 minutes. Samples were prepared for gas chromatographic analysis according to the following procedure: 0.1±0.001 g of sample, 200.0 μl ISTD solution (1% by volume of decane in pyridine) and 1.0 ml of BSTFA (N,O-bis(tri-methylsilyl)trifluoroacetamide) with 1% TMSCl (trimethylchlorosilane) were heated in a vial at 80° C. for 30 minutes to ensure complete derivatization. A 0.5-μl sample of this derivatized solution was injected for GC analysis.

For a typical crude reaction product, 26 species were identified using GC/MS. For the example of propionic acid as the carboxylic acid, the desired products are methyl glycolate (MG), glycolic acid (G1) and its oligomers (Gn, n=2-5) and 2-propionoxyacetic acid (A3 GH) and its oligomers (A3GnH, n=2-4). Identified co-products include formic acid (A1), and diglycolic acid (DG). Unreacted starting materials are in the form of free formaldehyde (F0), methylene glycol (F1) and polymethylene glycol (Fn, n=2-10).

Gas Chromatography (GC) Method 2. The components of samples were first reacted with BSTFA in the presence of pyridine to the corresponding TMS-derivatives including water, which were then separated and quantified by an internal standard (decane or dodecane) wt % calibrated GC method. The volume ratio of sample to derivatization reagent (BSTFA) and pyridine (containing the internal standard compound) was 0.1 g: 1 ml:0.2 ml in a GC vial, which was heated at 80° C. for 30 minutes to ensure complete derivatization. The GC method uses a DB-1301 capillary column or equivalent (6% cyanopropylphenyl/94% dimethylpolysiloxane stationary phase, 60 meters×0.32 mm ID×1.0 um film thickness), a split injector (at 280° C.), a flame ionization detector (at 300° C.), helium carrier gas at a constant linear velocity of 27 cm/sec (a Shimadzu GC 2010 or equivalent) or at an initial column head pressure of 17 psig, an oven temperature program of 80° C. initial temp for 6 min, 4° C./min temp ramp to 150° C. held for 0 min and 10° C./min temp ramp to 290° C. for 17.5 min final hold time. 1 μl of the prepared sample solution was injected with a split ratio of 40:1 Analytes include: MeOH, A1, water, heptane, toluene, G1 and higher oligomers, A5 GH and higher oligomers, DG, methyl valerate, and MG.

High Pressure Liquid Chromatography (HPLC) Method 1. Samples were prepared by pipetting 100 μl of sample into a 10 mL volumetric flask, adding a few mLs of water, ten drops of conc. H₃PO₄, and diluting to the mark with water. An aliquot of sample was injected onto an Agilent 1100 HPLC instrument for analysis using a BIORAD Fast Acid Analysis Column (100×7.8 mm) at 60° C. The sample is eluted using 10 mM sulfuric acid in water with a flow rate of 1 mL/min. Glycolic acid was detected at 210 nm on the UV detector. An external standard was used for calibration along with a dilution factor in a sequence table. The results are reported as ppm using a two-level calibration curve (100 and 1000 ppm) for each acid.

High Pressure Liquid Chromatography (HPLC) Method 2. Glycolic acid concentration was quantitatively determined by an Agilent 1100 HPLC using a Hamilton PRP-X300 exclusion column (250×4.1 mm). Glycolic acid was detected at 210 nm on the UV detector. Two eluents were used, where eluent A is 5 mM H₃PO₄ in 1% acetonitrile/99% water and eluent B is 5 mM H₃PO₄ in 10% acetonitrile/90% water. The following gradient was used: 100% A for 2 min; →100% B 5 min; Hold for 3 mins; →100% A 0.1 mins; equilibrate 4.9 mins for a total run time of 15 minutes. HPLC samples were prepared according to the following method. The samples of crude hydrocarboxylation reaction are hydrolyzed and diluted for analysis according to the following procedure: 200 mg of sample is weighed into a 10 mL volumetric flask, then 0.5 mL of 40% NaOH is added. After 10 minutes, 2 mL of water is added and the solution is allowed to sit for another 10 minutes. The solution is then diluted to the mark with water. A milliliter of this solution is then diluted tenfold before analysis.

High Pressure Liquid Chromatography (HPLC) Method 3. Samples were analyzed by liquid chromatography for glycolic acid using ion-exclusion chromatography after samples were subjected to acid hydrolysis in aqueous 25% v/v H₂SO₄ at 80° C. for 30 minutes. The analytes were separated on a Hamilton PRP X300 column using a 10 mM H₃PO₄ mobile phase with a 1-20% v/v acetonitrile gradient. The eluting components were monitored using a UV detector set at 210 nm and their concentrations calculated based on calibration using external standards. Formaldehyde was determined by liquid chromatographic separation of the 2,4-dinitrophenylhydrazone derivative of formaldehyde and its subsequent detection by UV at 360 nm. The same acid hydrolysate from the procedure above was reacted with dinitrophenylhydrazine, then analyzed using a Phenomenex Luna C8 column using a 1:1 water:acetonitrile mobile phase under isocratic conditions. The formaldehyde concentration was calculated based on calibration using external standards.

X-ray method for triflic acid. Reactor effluent and extraction samples were analyzed for sulfur using a wavelength dispersive x-ray fluorescence (WDXRF) semi-quantitative application called UNIQUANT™ (UQ). UQ affords standardless XRF analysis of samples. The data were mathematically corrected for matrix differences between calibration standards and samples as well as absorption and enhancement effects; i.e., inter-element effects. Instrument conditions for sulfur analysis were: Line, K_(a); kV, 40; mA, 60; Filter, none; Collimator Spacing (mm), 150; Crystal, Ge III-C; Peak Angle (2q), 110.6712; Detector, flow; PHD Lower, 35; PHD Upper, 70; Collimator Mask (mm), 30; Peak time (s), 30. Sulfur weight fraction numbers were converted to triflic acid weight equivalents by the factor 4.68 (ratio of molecular weight of triflic acid to that of sulfur).

Example 1

20% W-heteropoly/silica catalyst purchased from Johnson Matthey was used as received. A 50 mL Hastelloy 276C autoclave was heated with a heating block, with temperature control provided by feedback via a thermocouple in the autoclave thermowell. Pure carbon monoxide gas (>99.9%) was fed to the autoclave via a high pressure regulator. The autoclave was charged with the paraformaldehyde (3.12 g, 0.099 mol), propionic acid (30.74 g, 0.41 mol), 20% W-heteropoly/silica catalyst (1.9 g), assembled, and pressurized with 200 psig of nitrogen and vented. This purging procedure was repeated two times. To remove nitrogen from the autoclaves, they were purged with 200 psig of carbon monoxide. Then the reactors were pressurized with 200 psig of carbon monoxide and heated with stirring to 140° C. The reactor was then pressurized to 1000 psig carbon monoxide and the pressure was maintained from the surge tank. After a 2 hour hold time, the reactor was cooled to room temperature and vented. Finally the autoclave was purged with nitrogen and unloaded. The reaction content was analyzed by GC and/or HPLC. Table 2 gives the yield.

Examples 2-7

Example 1 was repeated using the catalyst and catalyst loading and hold time given in Table 2. The resulting yields are also given in Table 2.

For Examples 4 and 5, the AMBERLYST catalyst preparation was as follows. The resin was washed up-flow with six bed volumes of ambient temperature distilled water over a period of 15 minutes. The washed resins were then dried in a vacuum oven at 109° C. and placed in a desiccator until needed.

For Examples 6 and 7 the SMOPEX 101 catalyst preparation was as follows. To 20 g of SMOPEX catalyst, in 250 mL beaker, 50 mL of propionic acid was added. The catalyst was allowed to sit for 15 min and then filtered using vacuum filtration. The vacuum was turned off and 20 mL of propionic acid was passed through the catalyst. This step was repeated three times to ensure that all of the water was washed off of the catalyst. Finally the solid was dried under house vacuum overnight.

TABLE 2 Hydrocarboxylation of Paraformaldehyde in Propionic Acid Catalyzed by Strongly Acidic Solid Acid Catalysts. loading temp time yield EX catalyst (wt %) (° C.) (h) (%) 1 20% W-heteropoly/silica 5.1 140 2 2.1 2 SiO₂/Al₂O₃ 5 140 2 2.6 3 SAC-13 15 140 3 82.3 4 AMBERLYST 36 (5.4 mmol/g) 5.0 140 2 71.1 5 AMBERLYST 36 (5.4 mmol/g) 5.0 140 3 75.7 6 SMOPEX 101 (4% crosslinked) 5.0 140 3 61.4 7 SMOPEX 101 (12% crosslinked) 5.0 140 3 69.4

The following examples demonstrate the effect of pressure, temperature, and water content on the batch hydrocarboxylation of paraformaldehyde in propionic acid using a dry AMBERLYST 36 solid acid catalyst.

Example 8

A 300 ml Hastelloy 276C autoclave was charged with paraformaldehyde (15.99 g, 0.53 mol), dry AMBERLYST 36 catalyst (9.3 g), propionic acid (157.9 g, 2.13 mol), and formic acid (3.8 g). The autoclave was then assembled and pressurized with 200 psig of N₂ and vented. This purging procedure was repeated two times. The autoclave was purged with 200 psig carbon monoxide in order to remove N₂. The reactor was pressurized with carbon monoxide to 500 psig and heated with stirring to 100° C. Once the desired temperature was reached, the reactor was pressurized to 1500 psig carbon monoxide and the pressure of the autoclave was maintained from a surge tank. Samples of the reaction were taken over the duration of the experiment at approximately 0.5, 1, 1.5, 2, 2.5, and 3 hours. When the reaction time was complete, the reactor was cooled to room temperature and vented. The autoclave was purged with nitrogen and the product mixture removed. The samples were analyzed by GC. The temperature and pressure; the weight percent paraformaldehyde, propionic acid, and water; and the yield of desired products and selectivity are given in Table 3. The concentration of formic acid ranged from 2.2 weight percent to 2.4 weight percent.

Examples 9-32

Example 8 was repeated for examples 9-32 with no water, as in Example 8, or water (nominally 4.58 g, 0.5 eq.), or water (nominally 9.12 g, 1.0 eq.) with formic acid added at an amount of 2.0 wt % of the charged composition. The feed composition as well as the temperature and pressure of the reactor are as noted in Table 3. The temperature and pressure; the weight percent paraformaldehyde, propionic acid, and water; and the yield of desired products and selectivity are given in Table 3.

TABLE 3 Hydrocarboxylation of Paraformaldehyde in Propionic Acid Catalyzed by AMBERLYST 36D (4.6-4.8 wt %). Yield Tem- of desired Selec- Pressure perature Feed (wt %) Time products tivity EX (psig) (° C.) F0 A3 Water (h) (%) (%) 8 1,500 100 9.0 88.8 0.0 0.5 14 53 1.0 29 68 1.5 43 73 2.0 53 79 2.5 64 85 3.0 71 88 9 1,000 100 9.0 88.8 0.0 0.5 25 63 1.0 42 72 1.5 62 83 2.0 73 99 2.5 81 100 3.0 86 101 10 500 100 9.0 88.8 0.0 0.5 11 100 1.0 20 99 1.5 27 95 2.0 36 88 2.5 45 84 3.0 53 81 11 1,500 100 8.6 84.4 4.9 0.5 2 79 1.0 2 81 1.5 3 83 2.0 10 80 2.5 11 82 3.0 12 89 12 1,000 100 8.5 84.4 4.9 0.5 7 84 1.0 7 69 1.5 8 69 2.0 9 68 2.5 10 65 3.0 12 66 13 500 100 8.6 84.4 4.9 0.5 5 83 1.0 5 82 1.5 6 91 2.0 1 80 2.5 7 85 3.0 8 71 14 750 100 8.6 84.4 4.9 0.5 5 78 1.0 6 75 1.5 7 73 2.0 7 70 2.5 8 70 3.0 9 66 15 750 100 9.0 88.8 0.0 0.5 12 95 1.0 24 92 1.5 28 96 2.0 37 81 2.5 46 87 3.0 54 85 16 500 100 8.8 86.6 2.5 0.5 7 99 1.0 8 93 1.5 9 90 2.0 10 86 2.5 13 85 3.0 15 82 17 750 100 8.8 86.6 2.5 0.5 8 89 1.0 10 96 1.5 13 87 2.0 16 91 2.5 19 83 3.0 23 91 18 1000 100 8.8 86.6 2.5 0.5 6 102 1.0 7 113 1.5 7 108 2.0 7 104 2.5 9 101 3.0 12 82 19 1,500 100 8.8 86.6 2.5 0.5 10 80 1.0 13 79 1.5 17 79 2.0 20 80 2.5 24 80 3.0 28 80 20 1,500 100 9.0 88.8 0.0 0.5 17 94 1.0 31 81 1.5 44 82 2.0 58 89 2.5 68 90 3.0 75 92 21 500 100 9.0 88.8 0.0 0.5 9 73 1.0 12 87 1.5 17 85 2.0 21 81 2.5 24 81 3.0 28 81 22 1,500 100 8.6 84.4 4.9 0.5 4 27 1.0 4 28 1.5 5 28 2.0 6 24 2.5 6 24 3.0 7 26 23 500 100 8.5 84.4 4.9 0.5 1 77 1.0 6 87 1.5 6 80 2.0 6 80 2.5 7 75 3.0 8 76 24 1000 100 8.8 86.6 2.5 0.5 6 77 1.0 10 82 1.5 12 90 2.0 13 87 2.5 19 90 3.0 21 90 25 500 140 9.0 88.8 0.0 0.5 45 81 1.0 63 85 1.5 77 99 2.0 78 104 2.5 78 106 3.0 79 108 26 1,500 140 8.6 84.4 4.9 0.5 38 75 1.0 48 78 1.5 59 83 2.0 65 90 2.5 68 92 3.0 69 92 27 1,000 120 8.6 86.6 2.5 0.5 16 68 1.0 24 70 1.5 32 70 2.0 39 86 2.5 48 87 3.0 52 89 28 500 140 8.6 84.4 4.9 0.5 20 63 1.0 32 65 1.5 40 69 2.0 54 76 2.5 48 79 3.0 52 82 29 1,500 140 9.0 88.8 0.0 0.5 67 97 1.0 82 100 1.5 75 102 2.0 84 107 2.5 84 108 3.0 84 108 30 2,000 140 9.0 88.9 0.0 0.5 78 97 1.0 83 100 1.5 84 102 2.0 85 103 2.5 86 104 3.0 87 104 31 2,000 140 8.6 84.5 4.9 0.5 38 77 1.0 61 84 1.5 71 87 2.0 76 89 2.5 77 90 3.0 79 91 32 2,000 140 8.8 86.6 2.5 0.5 60 86 1.0 72 91 1.5 78 93 2.0 80 94 2.5 79 95 3.0 80 95

The following examples demonstrate the hydrocarboxylation of paraformaldehyde using a triflic acid catalyst in acetic, propionic, n-butyric, i-butyric, valeric, and hexanoic acids.

Example 33

A 100 mL zirconium high pressure autoclave was fitted with an impeller, gas inlet tube, sample tube, and thermowell. The autoclave was heated with a heating block, with temperature control provided by feedback via a thermocouple in the autoclave thermowell. Pure carbon monoxide gas (>99.9%) was fed to the autoclave via a high pressure regulator. Triflic acid (0.562 g, 3.7 mmol), acetic acid (30.03 g, 0.5 mol) and paraformaldehyde (3.94 g, 0.125 mol) were added to the autoclave and sealed. The autoclave was secured to the stand and the system was purged with carbon monoxide and pressurized to 250 psig carbon monoxide. The temperature in the autoclave was increased to 140° C. while stirring at 1000 rpm. Upon reaching 140° C., the pressure in the autoclave was increased to 1,000 psig carbon monoxide. Once temperature and pressure were reached, a sample was taken, “time 0.” The pressure and temperature were maintained for 4 hours. Subsequent samples of the reaction were taken at approximately 15, 30, 45, 60, 90, 120, 180 and 240 minutes and analyzed by HPLC. Results are given in Table 4, in terms of yield of glycolic acid and selectivity.

Example 34

Example 33 was repeated except that propionic acid (37.04 g, 0.5 mol) was charged to the autoclave in place of acetic acid. Results are given in Table 4.

Example 35

Example 33 was repeated except that n-butyric acid (44.06 g, 0.5 mol) was charged to the autoclave in place of acetic acid. Results are given in Table 4.

Example 36

Example 33 was repeated except that i-butyric acid (44.06 g, 0.5 mol) was charged to the autoclave in place of acetic acid. Results are given in Table 4.

Example 37

Example 33 was repeated except that valeric acid (51.07 g, 0.5 mol) was charged to the autoclave in place of acetic acid. Results are given in Table 4.

Example 38

Example 33 was repeated except that hexanoic acid (58.08 g, 0.5 mol) was charged to the autoclave in place of acetic acid. Results are given in Table 4.

TABLE 4 Hydrocarboxylation of Paraformaldehyde in Carboxylic Acids Catalyzed by Triflic Acid. EX Carboxylic Acid Time (h) Yield (%) Selectivity (%) 33 Acetic Acid 0 14.1 79.2 0.3 45.9 92.0 0.5 84.1 93.5 0.8 92.8 96.5 1.0 97.2 95.8 1.3 96.5 95.8 1.8 98.9 97.1 3.0 98.3 99.4 4.0 99.9 98.2 34 Propionic Acid 0 7.5 45.1 0.3 28.1 74.6 0.5 59.9 87.1 0.8 74.1 89.7 1.0 76.4 90.6 1.5 81.9 92.4 2.4 85.9 94.0 2.8 84.9 94.8 4.0 83.4 94.2 35 n-butyric acid 0 10.2 74.9 0.3 40.8 87.1 0.5 70.0 94.2 0.8 90.8 97.5 1.0 89.9 97.2 1.3 97.3 97.9 1.8 101.1 97.6 3.0 104.4 98.3 4.0 104.1 98.2 36 i-butyric 0 9.8 67.6 0.3 21.7 78.8 0.5 40.1 82.6 0.8 46.9 84.7 1.0 52.7 86.8 1.5 57.8 88.5 2.4 67.0 92.5 2.8 66.8 92.3 4.0 65.6 93.3 37 Valeric Acid 0 9.5 64.5 0.3 28.4 72.6 0.5 55.0 87.2 0.8 69.1 92.2 1.0 82.9 100.0 1.3 94.4 99.5 1.8 96.0 100.0 3.0 99.3 98.5 4.0 100.8 100.0 38 Hexanoic Acid 0 7.9 42.2 0.3 20.9 55.0 0.5 41.7 71.4 0.8 54.5 77.5 1.0 65.0 83.3 1.3 73.9 87.9 1.8 77.9 92.9 3.0 81.8 94.2 4.0 84.5 97.2

For all extraction examples the partition coefficient for component A is defined as follows:

${P(A)} = \frac{{Weight}\mspace{14mu}{Percent}\mspace{14mu} A\mspace{14mu}{in}\mspace{14mu}{Hydrophobic}\mspace{14mu}{phase}}{{Weight}\mspace{14mu}{Percent}\mspace{14mu} A\mspace{14mu}{in}\mspace{14mu}{Hydrophilic}\mspace{14mu}{phase}}$

Extraction selectivity between components A and B is defined as: S(AB)=P(A)/P(B)

Example 39

A first standard aqueous acetic-glycolic acid solution was prepared by mixing glycolic acid, water, and acetic acid. Fifteen grams of this first standard solution was added to a separate glass vial along with fifteen grams of each of the nonpolar solvents listed in Table 5. A second standard aqueous propionic-glycolic acid solution was prepared and fifteen grams of this second standard solution was added to a separate glass vial along with fifteen grams of each of the nonpolar solvents listed in Table 5. The contents of each vial were mixed vigorously and allowed to settle and separate into two clear phases. All experiments were conducted at room temperature. The phases were analyzed by GC to determine acetic acid, propionic acid, and glycolic acid compositions. These analytical results were used to calculate partition coefficients and extraction selectivities. Results are summarized in Table 5. The partition coefficients and selectivities for propionic acid are higher than the corresponding values for acetic acid, thus illustrating the value of using propionic acid instead of acetic acid as a hydrocarboxylation solvent/reactant.

TABLE 5 Extraction Compositions, Partition Coefficients and Selectivities for Mixtures Containing Acetic Acid and Propionic acid. acid glycolic water solv. P P S (acid/ Ex. Solvent acid (g) (g) (g) (g) (acid) (glycolic) glycolic) 39a Toluene acetic 3.6 2.4 9 15 0.08 <0.001 >80 39b Heptane acetic 3.6 2.4 9 15 0.02 <0.001 >20 39c methyl acetic 3.6 2.4 9 15 0.80 0.14 6 propionate 39d MTBE acetic 3.6 2.4 9 15 1.00 0.07 14 39e Toluene propionic 3.6 2.4 9 15 0.70 <0.001 >70 39f Heptane propionic 3.6 2.4 9 15 0.10 <0.011 >10 39g methyl propionic 3.6 2.4 9 15 2.50 0.16 16 propionate 39h MTBE propionic 3.6 2.4 9 15 3.40 0.09 38

Examples 40-50

These examples illustrate the selective extractive separation of n-valeric, n-butyric (nHOBu), iso-butyric (1HOBu), and propionic (HOPr) acids from highly concentrated aqueous glycolic acid. Aqueous glycolic acid-water-carboxylic acid mixtures were prepared and added to separate glass vials along with the amount of each hydrophobic solvent as listed in Table 6. The contents of each vial were mixed vigorously and allowed to settle and separate into two clear phases. All experiments were conducted at room temperature. The phases were analyzed by GC to determine carboxylic acid and glycolic acid compositions. These analytical results were used to calculate partition coefficients and selectivities. Results are summarized in Table 6.

TABLE 6 Extraction compositions, Partition Coefficients and Selectivities. acid glycolic water solv. P P S (acid/ Ex. Solvent acid (g) (g) (g) (g) (acid) (glycolic) glycolic) 40 Toluene n-butyric 10 8 2 10 5.2 0.035 148.8 41 MTBE n-butyric 10 8 12 15 7.4 0.189 39.4 42 Heptane n-butyric 10 8 2 10 3.4 0.015 220.4 43 Toluene i-butyric 10 8 2 10 7.4 0.027 271.6 44 MTBE i-butyric 10 8 11 15 8.3 0.176 46.9 45 Heptane i-butyric 10 8 2 10 6.7 0.011 626.6 46 Toluene propionic 10 8 2 10 1.9 0.056 34.5 47 MTBE propionic 10 8 12 15 2.2 0.341 6.6 48 MIBK propionic 10 8 12 15 2.0 0.303 6.6 49 heptane n-valeric 8 6 2 4 8.2 0.0001 5,672.1 50 toluene n-valeric 8 6 2 4 13.5 0.030 446.6

Examples 51-58

These Examples illustrate the effect of glycolic acid content on the extractive separation of n-valeric acid from glycolic acid. Aqueous glycolic acid-water-n-valeric acid mixtures were prepared and added to separate glass vials along with the amount of toluene or heptane as listed in Table 7. The contents of each vial were mixed vigorously and allowed to settle and separate into two clear phases. All experiments were conducted at room temperature. The phases were analyzed by GC to determine n-valeric acid and glycolic acid compositions. These analytical results were used to calculate partition coefficients and selectivities as shown in Table 7.

TABLE 7 Extraction Compositions, Partition Coefficients and Selectivities. wt. % acid glycolic water solv. P P S Ex. solvent glycolic (g) (g) (g) (g) (acid) (glycolic) (acid/glycolic) 51 toluene 75 8 5.99 2.00 4.00 329 0.44 748.2 52 toluene 50 8.00 4.01 4.01 4.02 636 0.31 2,041.3 53 toluene 25 7.98 2.01 6.02 3.99 763 0.18 4,183.8 54 toluene 0 7.97 0.00 8.15 4.03 1,319 NA NA 55 heptane 75 8.09 6.06 2.02 4.04 8.0 0.006 1,419.3 56 heptane 50 8.02 4.05 4.05 4.01 12.4 0.006 2,099.0 57 heptane 25 8.11 2.01 6.04 4.04 15.0 0.004 3,767.9 58 heptane 0 8.03 0.00 8.02 4.19 18.9 NA NA

Examples 59-62

These Examples illustrate the effect of glycolic acid content on the extractive separation of valeric acid from triflic acid and glycolic acid. Aqueous glycolic acid-water-triflic acid mixtures were prepared and added to separate glass vials along with the amount of toluene and valeric acid as listed in Table 8. The contents of each vial were mixed vigorously and allowed to settle and separate into two clear phases. All experiments were conducted at a temperature of 50° C. The phases were analyzed by GC and X-ray to determine valeric, triflic acid, and glycolic compositions. These analytical results were used to calculate partition coefficients and selectivities as shown in Table 8.

TABLE 8 Extraction Compositions, Partition Coefficients and Selectivities of Valeric Acid, Triflic Acid and Glycolic Acid in Toluene. Acid glycolic water solv. triflic P P P S S Ex. (g) (g) (g) (g) (g) (acid) (glycolic) (triflic) (acid/glycolic) (acid/triflic) 59 1.07 0.00 9.72 9.00 0.30 13.7 NA 0.0002 NA 57,499 60 4.00 0.00 7.77 7.99 0.24 38.0 NA 0.001 NA 38,376 61 1.02 7.79 1.95 9.02 0.30 2.0 0.001 0.0001 1,388.1 20,302 62 4.03 6.23 1.56 8.03 0.24 4.2 0.031 0.0012 136.6 3,414

Example 63

A solution rich in esters of glycolic and valeric acids was prepared by mixing 1.45 moles of valeric acid per mole of glycolic acid. This mixture was heated to reflux under vacuum to remove approximately 0.2 grams of water per gram of glycolic acid fed, to give an average degree of oligomerization of 0.84 ester bonds per mole of glycolic acid (i.e., mostly A5 GH). This source of A5 GH was used in Examples 63 and 64.

A feed was produced by mixing the source of A5 GH above with triflic acid and heptane to give the feed composition listed in Table 9. This example illustrates a simulated continuous extraction of a feed containing esters of glycolic and valeric acids, triflic acid, and heptane with a hydrophilic solvent containing 20% aqueous glycolic acid for separation of Triflic acid from A5 GH. The feed mixture was subjected to a cascaded series of twenty-four cross-flow batch extractions to simulate a six-stage continuous counter-current extraction process, with the feed mixture (20.0 g) introduced on stage six (from the top) and the aqueous glycolic acid solvent (8.0 g) on stage one (top of extractor). The multi-cycle, cascaded pattern of 24 extractions in which one feed mixture charge is added into the first cycle of the cascade, and multiple hydrophilic solvent charges are introduced into each cycle of the cascade, and with raffinate and extract compositions introduced to the next cycle of the cascade, results in a set of conditions on the final cycle which have been shown to closely approach the equilibrium composition profile of a continuous, staged, counter-current fractional extractor. For this work, three cycles were found to be sufficient to asymptotically approach continuous extraction equilibrium conditions. The simulated counter-current extraction technique used herein is well-known to those skilled in the art and is laid out in detail in Treybal (“Liquid Extraction,” 2nd Ed., McGraw-Hill Book Company, New York, N.Y., 1963, pp. 349-366). The feed contained 10 weight percent hydrophobic solvent. The hydrophilic solvent (aqueous glycolic acid) to feed (including the heptane) weight ratio was 0.4:1.0. The experiment was conducted at room temperature. The final simulated raffinate (19.24 g—top product) and extract (8.58 g—bottom product) streams were subjected to GC and X-ray analysis to determine the compositions of the products. Results are given in Table 9 with all percentages representing weight percent. The percent recovery to the extract is based on the amount of each component in all inputs to the extractor. The percent accountability of each component is equal to total out/total in as a percentage.

TABLE 9 Simulated Extraction Results Aq G1 Recovery Solvent Feed Extract Raffinate % to Extract (%) (%) (%) (%) Account (%) Water 80.0 2.1 59.9 7.4 97 78.2 Heptane 0.0 10.0 0.3 10.1 99 1.2 A5 0.0 46.5 13.1 45.1 106 11.4 G1 20.0 3.5 14.1 5.6 100 52.4 A5GH 0.0 29.0 5.6 27.1 99 8.4 G2 0.0 1.1 1.0 0.1 48 86.5 A5G2H 0.0 4.2 0.2 3.5 81 2.6 Triflic 0.0 2.0 4.6 0.0 100 99.2 Other 0.0 1.7 1.2 1.2 90 32.3

Example 64

Example 63 was repeated using a feed produced by mixing the source of A5 GH above with triflic acid to give the feed composition listed in Table 10 with the feed (20.0 g) introduced on stage three (from the top), the hydrophobic solvent (10.0 g), toluene, introduced on stage six (from the top), and the hydrophilic solvent or water wash (8.0 g) introduced on stage one (from top). The final simulated raffinate (11.4 g—hydrophobic product) and extract (26.6 g—hydrophilic product) streams were subjected to GC and X-ray analysis to determine the compositions of the products. Results are given in Table 10.

TABLE 10 Simulated Extraction Results Hydro- Hydro- Hydro- Hydro- philic phobic philic phobic % Solvent Solvent Product Product Recovery Feed (%) (%) (%) (%) to extract Toluene 0.00 100.0 0.23 37.32 0.26 Water 1.26 100.0 69.53 8.37 78.07 Triflic 2.20 3.83 <0.001 >99.94 G1 5.47 25.22 0.43 96.16 A5 39.16 0.72 23.51 1.30 A5GH 50.58 0.06 29.86 0.09 other 1.33 0.41 0.51 not determined TOTAL 100.0 100.0 100.0 100.0 100.0%

Example 65

Example 65 illustrates a continuous extraction demonstration of the recovery of triflic acid from a esters of glycolic and valeric acids feed stream derived from the hydrocarboxylation of formaldehyde using a hydrophilic solvent comprising 70 wt % G1, 30 wt % water and a hydrophobic solvent comprising 100 wt % toluene. This extraction was carried out in a Karr column comprising four jacketed glass column sections (15.9 mm inside diameter, each 501 mm in length) stacked on top of each other. Jacketed glass disengagement sections, 25.4 mm inside diameter and 200 mm in length, were attached to the top and bottom of the four extractor sections. The four column sections and two disengagement sections were joined together with Teflon O-ring gaskets (25 mm thickness) held together with bolted flanges to form the column body. Feed ports were fitted into each Teflon O-ring to allow change of feed locations. The total height of the resulting column was approximately 2.6 meters. Separate temperature-controlled heating baths were connected to the jacket of each disengagement zone and one bath to the combined four column sections to maintain the desired extraction temperature gradient.

Agitation in the column was supplied by an 3.2 mm diameter Hastelloy 276C impeller shaft fitted with seventy-seven Teflon plates, each with eight radial rectangular petals (to provide gaps for liquid flow paths), spaced 25 mm apart in the column sections. The impeller shaft was attached at the top of the extractor to an electric motor fitted with a concentric gear to convert rotational motion into reciprocal motion. The agitator stroke length (i.e., extent of vertical motion) was 19 mm, and varied from 200 to 350 strokes per minute.

Depending on the chosen continuous phase, the liquid-liquid phase interface was maintained in either the top or bottom disengagement section (in the top section if the less dense phase were continuous, bottom section if the more dense phase were continuous) by visual observation and manual manipulation of the underflow take-off pump.

Up to three feeds could be supplied to the column via piston pumps from independently temperature-controlled jacketed glass vessels of four liter, two liter, and two liter volumes, while the underflow (more dense) product and the top, overflow (less dense) product were collected in two-liter glass vessels. The top product collected by gravity overflow from the upper disengagement section, while the bottoms product flow was controlled by a variable rate piston pump.

Feed locations are designated as follows from the top of the column to the bottom:

F1: Feed location between top disengagement zone and 1st column section

F2: Feed location between 3^(rd) and 4^(th) column sections

F3: Feed location between 4^(th) column section and bottom disengagement zone

The column was operated continuously for five hours. The feed was the combined crude hydrocarboxylation reactor product produced in Examples 137 and 138 discussed below. The crude hydrocarboxylation reactor product was fed at feed location F2, the hydrophilic solvent (70% glycolic acid and 30 wt % water) fed at F1 and the hydrophobic solvent fed at F3. The hydrophilic solvent to feed ratio was held at 0.124 to 1 on a mass basis, and the hydrophobic solvent to valerate-triflic feed mass ratio was held at 0.59. These conditions resulted in greater than 99.0% of the triflic acid being recovered in the polar extract (aqueous extract). Results from this extraction are tabulated below in Table 11. All values are in weight percent.

Triflic acid is recovered in the hydrophilic product stream (extract) at a rate of 99%. About 21.2% of all G1 moieties in the valerate-triflic feed and hydrophilic solvent were recovered to the hydrophobic raffinate phase, but subtracting out G1 entering in the hydrophilic solvent, the recovery of G1 moieties in the valerate-triflic feed rises to 68.3%. Furthermore, since the original feed to the hydrocarboxylation reaction resulting in the crude hydrocarboxylation product from Examples 137 and 138, contained G1, the extraction actually resulted in essentially complete recovery of new G1 moieties created in the reaction Examples 137 and 138. Thus, such an extraction is capable of fully separating triflic acid from valerate-glycolic esters and producing a concentrated triflic acid-glycolic acid stream suitable for recycle to hydrocarboxylation.

TABLE 11 Karr Column Continuous Extraction Re- Hydro- Hydro- Hydro- Hydro- Mass covery philic phobic philic phobic Bal- to Feed Solvent Solvent Extract Raffinate ance Extract Triflic 2.93 7.74 0.023 100.4 99.0% Acid G1 13.30 70 46.40 3.50 100.9 78.8% DGA 5.40 13.30 1 117.5 78.8% A5 37 6.80 25.50 99.5 7.0% A5GH 26 6.30 17.50 99.5 9.2% A5G2H 7 1.40 5.07 104.8 7.2% A5G3H 2 0.40 1.26 92.1 8.2% Others 1.47 7.36 0.06 193.6 97.3% Water 4.90 30% 10.30 3.55 100.3 44.8% Toluene 100% 3.60 42.54 99.0 2.3% Total 100.0 100.0 100% 100.0 100.0 100.3 Flow- 10.5 1.3 6.2 3.95 14.1 rate, g/min

The following examples illustrate the hydrocarboxylation of either MDA in acetic acid or MDP in propionic acid catalyzed by strongly acidic solid acid catalysts.

Example 66

MDA (methylene diacetate) or MDP (methylene dipropionate) used in the following Examples were produced from a refluxing mixture of paraformaldehyde and acetic or propionic anhydride in the presence of a small amount of sulfuric acid. The reactions were followed by gas chromatography. Upon completion of the reaction, sodium acetate (NaOAc) or propionate were added to the mixture to neutralize the sulfuric acid. The mixture was distilled to give 99% pure methylene dicarboxylate. The following procedure for methylene diacetate is exemplary: A 5 L round-bottom flask was fitted with a condenser, thermowell, overhead stirrer, inert gas bubbler, and heating mantle. To this flask was added 885 grams of paraformaldehyde followed by 3,324 mL of acetic anhydride. The mixture was then stirred at room temperature and 12 mL of concentrated sulfuric acid was added. An exotherm heated the solution to approximately 80° C. and then the heating mantle was turned on. The mixture was held at reflux for almost 10 hours and sampled periodically to check for completion by gas chromatography. Upon completion, 35 g of NaOAc was added to the mixture to neutralize the sulfuric acid. The mixture was then transferred to another flask along with the NaOAc and pure MDA was distilled.

Example 67

A 50 mL Hastelloy 276C high pressure autoclave was fitted with an impeller, gas inlet tube, sample tube, and thermowell. The autoclave was heated with a heating block, with temperature control provided by feedback via a thermocouple in the autoclave thermowell. Pure carbon monoxide gas (>99.9%) was fed to the autoclave via a high pressure regulator. The autoclave was charged with 20% W-heteropoly/silica catalyst (1.48 g) propionic acid (12.28 g, 0.16 mol) and MDP (14.1 g, 0.08 mol) and water (1.4 g, 0.08 mol) and sealed. The autoclave was secured to the stand and the system was pressurized with 200 psig nitrogen and vented. This purging procedure was repeated two times. The autoclave was then purged with carbon monoxide and pressurized to 200 psig carbon monoxide. The temperature in the autoclave was increased to 140° C. Upon reaching 140° C., the pressure in the autoclave was increased to 1,000 psig carbon monoxide. The reaction was held at these conditions for 2 hours and then cooled to room temperature and vented. Finally the autoclave was purged with nitrogen and unloaded. The reaction contents were analyzed by GC. Results are shown in Table 12.

Examples 68-83

The procedure of Example 67 was repeated using either MDP/propionic acid or MDA/acetic acid and water at target equivalents of 1 eq. of MDA(MDP), 2 eq. acetic (propionic) acid, and 1 eq. water at a reaction pressure of 1000 psig carbon monoxide. The examples were run with the solid catalyst and corresponding loading, at the temperature, and for the holding time shown in Table 12. Calculated yields are also given in Table 12.

TABLE 12 Hydrocarboxylations of Methylene Diacetate (MDA) or Methylene Dipropionate (MDP) Catalyzed by Strongly Acidic Solid Acid Catalysts. loading temp time yield EX catalyst (wt %) (° C.) (h) (%) 67 MDP 20% W-heteropoly/silica 5 140 2 6.5 68 MDP SiO₂/Al₂O₃ 5 140 2 2.0 69 MDA K10 5 140 2 3.8 70 MDA AMBERLYST 70 5 140 2 18.8 71 MDA SAC-13 9 140 1 47.8 72 MDA SAC-13 9 160 1 69.8 73 MDA SAC-13 9 180 1 78.8 74 MDA Nafion NR50 5 140 2 69.4 75 MDA SAC-13 15 160 1 98.6 76 MDA polymer-bound pTSA 5 140 2 66 77 MDA AMBERLYST 36 5 140 2 77 78 MDA SMOPEX (4% crosslinking) 5 140 3 65 79 MDA SMOPEX (8% crosslinking) 5 160 2 70 80 MDA SMOPEX (12% crosslinking) 5 180 2 66 81 MDP AMBERLYST 36 5 140 2 86 82 MDP SAC-13 10 140 2 76 83 MDP SMOPEX (4% crosslinking) 5 140 2 68

Examples 84

A 50 mL Hastelloy 276C high pressure autoclave was fitted with an impeller, gas inlet tube, sample tube, and thermowell. The autoclave was heated with a heating block, with temperature control provided by feedback via a thermocouple in the autoclave thermowell. Pure carbon monoxide gas (>99.9%) was fed to the autoclave via a high pressure regulator. The autoclave was charged with AMBERLYST 36 D catalyst (1.43 g), propionic acid (12.3 g, 0.166 mol), MDP (14.1 g, 0.088 mol), and water (1.5 g, 0.083 mol) and sealed. The autoclave was secured to the stand and the system was pressurized with 200 psig nitrogen and vented. This purging procedure was repeated two times. The autoclave was then purged with carbon monoxide and pressurized to 500 psig carbon monoxide. The temperature in the autoclave was increased to 140° C. Upon reaching 140° C., the pressure in the autoclave was increased to 1,000 psig carbon monoxide. The reaction was held at these conditions for 2 hours and then cooled to room temperature and vented. Finally the autoclave was purged with nitrogen and unloaded. The reaction contents were analyzed by GC. The results are shown in Table 13.

Examples 85-91

Example 84 was repeated with the catalyst and catalyst loading and amount of propionic acid and water given in Table 13. Each reaction was run at 1000 psig carbon monoxide and at the temperature and for the time indicated in Table 13. Yield to desired products and selectivity are also given in Table 13.

TABLE 13 Hydrocarboxylations of MDP Loading A3 Water Temp Time Yield Select. Ex Catalyst (wt %) (eq) (eq) (° C.) (h) (%) (%) 84 AMBERLYST 5 2.0 1.0 140 2 96 96 36 D 85 AMBERLYST 8 0.14 1.1 140 2 89 94 36 D 86 AMBERLYST 5 2.1 1 140 2 86 96 36 D 87 AMBERLYST 5 1.1 1 140 2 78 95 36 D 88 AMBERLYST 5 0.15 1 140 2 72 94 36 D 89 AMBERLYST 5 2 0.05 140 2 2 28 36 D 90 AMBERLYST 5 2 0.05 90 2 3 5 36 D 91 AMBERLYST 5 2 0.5 140 2 16 66 36 D

The following examples illustrate the hydrocarboxylation of MDA in acetic acid catalyzed by various strongly acidic homogeneous catalysts. MDA was prepared as described above in Example 66.

Example 92

To a Hastelloy 276C 300 mL autoclave equipped with a liquid sampling loop and a high pressure addition funnel was added acetic acid (60.05 g, 1.0 mol), water (9.0 g, 0.5 mol), and trifluoromethanesulfonic acid catalyst (0.375 g, 2.5 mmol). The autoclave was heated with a heating block, with temperature control provided by feedback via a thermocouple in the autoclave thermowell. Pure carbon monoxide gas (>99.9%) was fed to the autoclave via a high pressure regulator. The MDA (66.26 g, 0.5 mol) was added to the addition funnel (blowcase). The autoclave was sealed, flushed with CO and heated to 140° C. under 100 psig carbon monoxide. The addition funnel containing the MDA was heated to 100° C. Upon reaching 140° C. in the autoclave, the MDA was charged to the autoclave by pressurizing the addition funnel. Immediately upon completing the liquid addition, a sample was removed from the autoclave (time zero) and the pressure was adjusted to 1000 psig CO. The temperature and pressure were maintained using pure carbon monoxide for the duration of the 4 hour reaction. Samples were removed from the autoclave at 15 min, 30 min, 45 min, 60 min, 120 min, 180 min and 240 min. The samples were analyzed by GC and HPLC. Final conversion and selectivity is given in Table 14.

Examples 93-96

Example 92 was repeated except the acid catalyst and amount were as given in Table 14. 2.5 mmol of acid catalyst was used in each case. The final MDA conversions and selectivities are given in Table 14.

TABLE 14 Hydrocarboxylation of MDA in Acetic Acid with a Homogeneous Strong Acid Catalyst. Catalyst MDA charge Con- MDA Ex. Catalyst (g) version Selectivity 92 trifluoromethanesulfonic acid 0.375 99 96 93 tetrafluoroethanesulfonic acid 0.455 96 96 94 bis(trifluoromethane)sulfonylamide 0.70 99 95 95 nonafluorobutanesulfonic acid 0.75 99 95 96 sulfuric acid 0.256 81 53

The following examples illustrate the effect of feed water content, temperature, pressure, and catalyst level on the hydrocarboxylation of trioxane or paraformaldehyde with valeric acid and glycolic acid as solvents/reactants and triflic acid as catalyst.

Example 97

The continuous hydrocarboxylation was carried out using a reactor system containing Hastelloy 276C autoclave (125 ml nominal volume) and associated feed and product storage equipment. The high pressure autoclave was fitted with a hollow shaft Rushton turbine impeller (for gas introduction and dispersion), baffles, thermowell, gas inlet tube, and sip tube to maintain liquid level at approximately 90 ml and to provide an exit for product effluent. The autoclave was heated electrically by a band heater, with temperature control provided by feedback via a K-type thermocouple in the autoclave thermowell.

Pure carbon monoxide gas (>99.9%) was fed to the autoclave via a high pressure flow controller. The gas entered the body of the autoclave via groves in the impeller bearings. The off gas flow rate was monitored by a dry bubble-type flow meter. The flow rates of the two liquid feeds were controlled to a precision of 0.001 ml/min with double-barreled 500 ml high-precision syringe pumps connected to stirred feed vessels.

Reactor effluent passed through heated Hastelloy tubing, an automatic pressure control valve (research control valve), and into a 1.0 L heatable Hastelloy collection vessel. The effluent collection vessel was fitted with a chilled coiled condenser. The gas outlet from the effluent tank was connected to a manual back pressure regulator to maintain vessel pressure at 40-100 psig. Temperatures, pressures, and other relevant system parameters were recorded automatically by a distributed control system.

Feed 1 (0.4 g/min) and Feed 2 (0.39 g/min), having the composition given in Table 15 were fed to the reactor. Carbon monoxide was fed at a rate of 998 SCCM as noted in Table 16. The reaction was run at a pressure of 1500 psig and a temperature of 170° C. with a residence time of 85 minutes. Table 16 also gives feed molar ratios and the source of formaldehyde. For Example 107 the source was trioxane.

Samples of the hydrocarboxylation reaction were analyzed by HPLC. Conversion, space-time yield, and selectivity of reacted formaldehyde to end products are summarized in Table 17. Any glycolic acid fed was subtracted out for conversion and yield calculations. Methanol was present as free methanol, methyl glycolate, and methyl valerate, and was converted to free methanol, glycolic acid, and valeric acid by the analytical method.

Examples 98-143

Example 97 was repeated with the liquid feeds given in Table 15, the carbon monoxide flow rate, source of formaldehyde, feed molar ratios, pressure, temperature, residence time given in Table 16. Conversion, space-time yield, and selectivity of reacted formaldehyde to end products are summarized in Table 17.

TABLE 15 Feed 1 and Feed 2: Rates and Compositions Feed 1, mass % Feed 2 mass % Ex # Feed 1 g/min F0 A5 G1 water Triflic Feed 2 g/min A5 Triflic 97 0.40 21.1 71.9 0.0 3.8 3.2 0.39 100.00 0.00 98 0.39 21.1 71.9 0.0 3.8 3.2 0.39 100.00 0.00 99 0.39 21.1 71.9 0.0 3.8 3.2 0.39 100.00 0.00 100 0.39 21.1 71.9 0.0 3.8 3.2 0.39 100.00 0.00 101 0.39 21.1 71.9 0.0 3.8 3.2 0.39 100.00 0.00 102 0.39 21.1 71.9 0.0 3.8 3.2 0.39 100.00 0.00 103 0.39 21.1 71.9 0.0 3.8 3.2 0.39 100.00 0.00 104 0.61 21.1 71.9 0.0 3.8 3.2 0.62 100.00 0.00 105 0.61 21.1 71.9 0.0 3.8 3.2 0.62 100.00 0.00 106 0.39 21.1 71.9 0.0 3.8 3.2 0.39 100.00 0.00 107 0.61 21.1 71.9 0.0 3.8 3.2 0.62 100.00 0.00 108 0.39 21.8 74.2 0.0 3.9 0.0 0.39 95.78 4.22 109 0.39 21.8 74.2 0.0 3.9 0.0 0.39 95.78 4.22 110 0.39 21.8 74.2 0.0 3.9 0.0 0.39 95.78 4.22 111 0.39 21.8 74.2 0.0 3.9 0.0 0.39 95.78 4.22 112 0.39 21.8 74.2 0.0 3.9 0.0 0.39 95.78 4.22 113 0.64 26.8 68.4 0.0 4.8 0.0 0.17 85.01 14.99 114 0.64 26.8 68.4 0.0 4.8 0.0 0.17 85.01 14.99 115 0.64 26.8 68.4 0.0 4.8 0.0 0.17 85.01 14.99 116 0.64 26.8 68.4 0.0 4.8 0.0 0.17 85.01 14.99 117 0.64 26.8 68.4 0.0 4.8 0.0 0.17 85.01 14.99 118 0.68 23.7 0.0 60.0 9.9 6.4 0.36 100.00 0.00 119 0.68 23.7 0.0 60.0 9.9 6.4 0.36 100.00 0.00 120 0.68 23.7 0.0 60.0 9.9 6.4 0.36 100.00 0.00 121 0.68 23.7 0.0 60.0 9.9 6.4 0.32 100.00 0.00 122 0.68 23.7 0.0 60.0 9.9 6.4 0.36 100.00 0.00 123 0.68 23.7 0.0 60.0 9.9 6.4 0.36 100.00 0.00 124 0.43 34.0 0.0 51.7 14.3 0.0 0.52 92.93 7.07 125 0.43 34.0 0.0 51.7 14.3 0.0 0.52 92.93 7.07 126 0.43 34.0 0.0 51.7 14.3 0.0 0.52 92.93 7.07 127 0.43 34.0 0.0 51.7 14.3 0.0 0.52 92.93 7.07 128 0.43 34.0 0.0 51.7 14.3 0.0 0.52 92.93 7.07 129 0.43 34.0 0.0 51.7 14.3 0.0 0.52 92.93 7.07 130 0.43 34.0 0.0 51.7 14.3 0.0 0.52 92.93 7.07 131 0.65 25.1 0.0 63.6 4.5 6.8 0.38 100.00 0.00 132 0.65 25.1 0.0 63.6 4.5 6.8 0.38 100.00 0.00 133 0.65 25.1 0.0 63.6 4.5 6.8 0.38 100.00 0.00 134 0.65 25.1 0.0 63.6 4.5 6.8 0.38 100.00 0.00 135 0.65 25.1 0.0 63.6 4.5 6.8 0.38 100.00 0.00 136 0.65 25.1 0.0 63.6 4.5 6.8 0.38 100.00 0.00 137 0.47 32.5 0.0 61.7 5.8 0.0 0.54 92.61 7.39 138 0.47 32.5 0.0 61.7 5.8 0.0 0.54 92.61 7.39 139 0.47 32.5 0.0 61.7 5.8 0.0 0.54 92.61 7.39 140 0.47 32.5 0.0 61.7 5.8 0.0 0.54 92.61 7.39 141 0.47 32.5 0.0 61.7 5.8 0.0 0.54 92.61 7.39 142 0.47 32.5 0.0 61.7 5.8 0.0 0.54 92.61 7.39 143 0.47 32.5 0.0 61.7 5.8 0.0 0.54 92.61 7.39%

TABLE 16 Overall Feed Molar Ratios and Reaction Conditions CO Res Flow F0 Feed Molar Ratio Press Temp Time Ex SCCM Type HFR A5 G1 Water Triflic Psig Celsius min 97 998.0 Trioxane 1.0 2.0 0.0 0.3 0.030 1500 170 85 98 998.0 Trioxane 1.0 2.0 0.0 0.3 0.030 1001 170 87 99 998.0 Trioxane 1.0 2.0 0.0 0.3 0.030 1498 160 87 100 998.0 Trioxane 1.0 2.0 0.0 0.30 0.030 1501 150 87 101 998.0 Trioxane 1.0 2.0 0.0 0.30 0.030 747 160 87 102 998.0 Trioxane 1.0 2.0 0.0 0.30 0.030 997 160 87 103 998.0 Trioxane 1.0 2.0 0.0 0.30 0.030 1500 170 87 104 998.0 Trioxane 1.0 2.0 0.0 0.30 0.030 749 150 55 105 998.0 Trioxane 1.0 2.0 0.0 0.30 0.030 750 140 55 106 998.0 Trioxane 1.0 2.0 0.0 0.30 0.030 753 170 87 107 998.0 Trioxane 1.0 2.0 0.0 0.30 0.030 751 150 55 108 998.0 Trioxane 1.0 2.0 0.0 0.30 0.030 1501 143 87 109 998.0 Trioxane 1.0 2.0 0.0 0.30 0.030 1495 160 87 110 998.0 Trioxane 1.0 2.0 0.0 0.30 0.030 1498 170 87 111 998.0 Trioxane 1.0 2.0 0.0 0.30 0.030 1500 170 87 112 998.0 Trioxane 1.0 2.0 0.0 0.30 0.030 1499 170 87 113 998.0 Trioxane 1.0 1.0 0.0 0.30 0.030 1498 170 87 114 998.0 Trioxane 1.0 1.0 0.0 0.30 0.030 1003 170 87 115 998.0 Trioxane 1.0 1.0 0.0 0.30 0.030 499 170 87 116 998.0 Trioxane 1.0 1.0 0.0 0.30 0.030 999 160 87 117 998.0 Trioxane 1.0 1.0 0.0 0.30 0.030 506 165 87 118 998.0 PF 1.0 0.7 1.0 0.70 0.054 1497 180 80 119 998.0 PF 1.0 0.7 1.0 0.70 0.054 1503 180 80 120 998.0 PF 1.0 0.7 1.0 0.70 0.054 1497 180 80 121 998.0 PF 1.0 0.7 1.0 0.70 0.054 1498 180 83 122 998.0 PF 1.0 0.7 1.0 0.70 0.054 1504 180 80 123 998.0 PF 1.0 0.7 1.0 0.70 0.054 1504 180 80 124 998.0 PF 1.0 1.0 0.6 0.70 0.054 1492 180 80 125 998.0 PF 1.0 1.0 0.6 0.70 0.054 1003 180 80 126 998.0 PF 1.0 1.0 0.6 0.70 0.054 500 180 80 127 998.0 PF 1.0 1.0 0.6 0.70 0.054 995 170 80 128 998.0 PF 1.0 1.0 0.6 0.70 0.054 502 170 80 129 998.0 PF 1.0 1.0 0.6 0.70 0.054 1000 160 80 130 998.0 PF 1.0 1.0 0.6 0.70 0.054 498 160 80 131 498.0 PF 1.0 0.7 1.0 0.30 0.054 1507 170 80 132 498.0 PF 1.0 0.7 1.0 0.30 0.054 1499 180 80 133 498.0 PF 1.0 0.7 1.0 0.30 0.054 1503 180 80 134 498.0 PF 1.0 0.7 1.0 0.30 0.054 1498 180 80 135 498.0 PF 1.0 0.7 1.0 0.30 0.054 1003 160 80 136 498.0 PF 1.0 0.7 1.0 0.30 0.054 1501 170 80 137 498.0 PF 1.0 1.0 0.8 0.30 0.054 1500 180 76 138 498.0 PF 1.0 1.0 0.8 0.30 0.054 999 180 76 139 498.0 PF 1.0 1.0 0.8 0.30 0.054 500 180 76 140 498.0 PF 1.0 1.0 0.8 0.30 0.054 999 170 76 141 498.0 PF 1.0 1.0 0.8 0.30 0.054 500 170 76 142 498.0 PF 1.0 1.0 0.8 0.30 0.054 1004 160 76 143 498.0 PF 1.0 1.0 0.8 0.30 0.054 500 160 76

TABLE 17 Selectivity, Conversion, and Space-Time Yield Results Space Time Molar % F0 Yield Selec- Exam- Con- gmol/ tivity ple version l-hr G1 A1 DG MGH MeOH 97 94.7 1.51 96.42 1.02 1.55 0.00 1.02 98 93.0 1.44 96.71 0.93 1.42 0.00 0.93 99 93.5 1.42 96.41 1.23 1.13 0.00 1.23 100 92.5 0.93 96.22 1.36 1.06 0.00 1.36 101 87.1 1.36 96.17 1.41 0.80 0.43 1.19 102 90.3 1.32 96.92 1.09 0.91 0.00 1.09 103 96.3 1.37 96.90 0.87 1.36 0.00 0.87 104 75.3 1.59 91.30 3.85 0.99 0.00 3.85 105 56.3 1.22 85.32 7.16 0.10 0.50 6.91 106 89.4 1.41 96.55 1.05 1.34 0.00 1.05 107 67.5 1.89 92.15 3.56 0.72 0.00 3.56 108 86.2 1.42 94.31 2.33 0.98 0.12 2.26 109 91.3 1.55 96.12 1.26 1.36 0.00 1.26 110 93.5 1.60 96.32 1.05 1.58 0.00 1.05 111 95.2 1.59 96.10 1.13 1.64 0.00 1.13 112 90.9 1.55 96.71 0.93 1.42 0.00 0.93 113 62.6 1.79 91.65 2.07 4.07 0.19 1.97 114 54.5 1.84 91.64 0.47 7.42 0.00 0.47 115 86.6 2.72 92.16 2.45 2.62 0.56 2.17 116 84.4 2.84 93.10 1.93 3.03 0.00 1.93 117 80.7 2.56 94.18 1.38 2.88 0.37 1.19 118 90.2 2.24 89.72 2.00 5.69 0.73 1.64 119 90.4 2.49 90.79 1.67 5.85 0.00 1.67 120 90.1 2.69 94.24 1.47 2.82 0.00 1.47 121 89.1 2.66 92.90 1.83 3.07 0.31 1.68 122 90.0 2.47 93.07 1.67 3.10 0.72 1.31 123 90.2 2.60 93.35 1.69 2.94 0.66 1.36 124 91.7 2.37 93.41 1.71 3.11 0.11 1.66 125 85.7 2.13 91.14 3.20 2.01 0.90 2.75 126 76.4 1.44 79.78 8.41 2.09 1.83 7.49 127 75.5 2.40 90.60 3.53 2.16 0.36 3.35 128 59.9 1.78 83.27 7.20 1.43 0.85 6.78 129 66.5 0.92 70.09 11.5 2.31 7.69 7.75 130 53.4 0.57 58.03 20.1 0.93 0.86 19.68 131 89.5 2.25 89.86 2.62 3.94 1.49 1.87 132 94.9 2.87 92.05 1.47 4.53 0.79 1.07 133 95.2 2.46 91.01 1.71 4.98 0.92 1.25 134 92.9 2.46 92.89 1.43 4.02 0.37 1.24 135 83.0 1.92 89.48 3.19 3.45 1.21 2.58 136 92.5 2.53 91.90 1.63 4.28 0.72 1.27 137 93.0 2.62 93.77 1.51 2.95 0.53 1.24 138 93.6 2.82 94.21 1.37 2.96 0.17 1.29 139 87.1 2.35 89.56 3.53 2.91 0.81 3.13 140 90.4 2.48 93.64 1.72 2.84 0.00 1.72 141 80.0 2.12 87.08 4.91 2.46 0.88 4.47 142 82.0 2.28 90.50 3.24 2.44 1.13 2.68 143 71.6 2.05 86.67 5.24 2.30 0.48 5.00

These examples illustrate the effect of feed water content, temperature, pressure, and catalyst level on the hydrocarboxylation of formaldehyde (trioxane) with triflic acid as catalyst, with n-butyric acid and glycolic acid as solvent/reactant.

Examples 144-147

Example 97 was repeated with only one feed at 0.91 g/min. The feed contained 14.6 wt % paraformaldehyde, 6.2% water, 28.8 wt % butyric acid, 48.2 wt % glycolic acid, and 2.2 wt % triflic acid. The feed molar ratio was paraformaldehyde (1.0), water (0.7), glycolic acid (1.5), and triflic acid (0.03). The hold-up time was 95 minutes. The feed rate of carbon monoxide was 498 SCCM. The operating pressure and temperature, along with conversion, space-time yield, and selectivity of reacted formaldehyde to end products are summarized in Table 18.

TABLE 18 Reactor Conditions, Selectivity, Conversion, and Space-Time Yield Results Space- Molar Time Temp Pres- % F0 Selec- Yield Cel- sure Con- tivity gmol/ Ex sius psig version G1 A1 MeOH MGH DG l-hr 144 150 935 40.1 70.1 13.9 13.9 0.0 2.2 1.04 145 170 1199 71.2 83.3 5.6 5.6 1.5 4.1 2.08 146 190 1199 88.3 89.6 1.8 1.8 1.6 5.2 2.91 147 170 1745 77.5 88.0 3.6 3.6 0.8 3.8 2.38

The following examples illustrate the effect of feed water content, temperature, pressure and catalyst level on the hydrocarboxylation of methylene diacetate with triflic acid as catalyst.

Examples 148-153

Example 97 was repeated but with MDA as the source of formaldehyde and at the feed rates and compositions noted in Table 19. In these experiments moles of MDA represent the formaldehyde equivalent, while acetic acid equivalents are calculated as the sum of free acetic acid fed and two times the MDA molar flow rate. The feed molar ratios, temperature, pressure, and hold-up time are given in Table 20. Conversion, space-time yield, and selectivity of reacted formaldehyde to end products are summarized in Table 21. All methanol was present as methyl acetate, and was also converted to free methanol and acetic acid by the analytical method.

TABLE 19 Feed 1 and 2 Rates and Compositions Feed 1 Feed 1, mass % Feed 2 Feed 2 mass % Ex g/min MDA A2 water g/min A2 water Triflic 148 0.69 100 0 0 0.71 86.7 1.3 0.30 149 0.69 100 0 0 0.79 69.5 29.2 1.30 150 0.69 100 0 0 0.79 69.5 29.2 1.30 151 0.69 100 0 0 0.79 69.5 29.2 1.30 152 1.10 56.4 7.7 35.9 0.32 99 0 1 153 0.03 56.4 7.7 35.0 0.32 96 0 4

TABLE 20 Overall Feed Ratios and Reaction Conditions Feed Molar Res Ratio Temp Press Time Ex F0 water A2 Triflic Celsius psig minutes 148 1.0 1.2 3.8 0.002 190 650 70 149 1.0 1.4 3.0 0.007 200 600 67 150 1.0 1.4 3.0 0.007 190 600 67 151 1.0 1.4 3.0 0.007 180 600 67 152 1.0 1.0 4.5 0.005 190 1300 69 153 1.0 1.0 4.5 0.020 170 1300 73

TABLE 21 Selectivity, Conversion, and Space-Time Yield Results % Molar Space-Time HFr Selectivity Yield Ex Conv G1 A1 MeOH MGH DG gmol/l-hr 148 70 95.8 1.75 1.75 0.00 0.85 2.20 149 75 90.8 1.7 1.7 0.00 5.8 2.00 150 70 94.2 1.5 1.5 0.00 2.8 2.00 151 50 92.9 1.8 1.7 0.3 3.1 1.20 152 77 93.1 1.7 1.3 0.7 3.1 2.60 153 95 93.3 1.7 1.4 0.7 2.9 2.80

The following examples illustrate the effect of feed water content, temperature, pressure, and catalyst level on the hydrocarboxylation of paraformaldehyde with sulfuric acid as catalyst.

Examples 154-159

Example 97 was repeated using only one feed stream with the feed rate and compositions shown in Table 22. The feed mixture was prepared by mixing, water, H₂SO₄ and HGH in a tank heated to 60° C. Paraformaldehyde was added with stirring until complete dissolution occurred. The feed was kept at 60° C. throughout the reaction period to ensure no solid formaldehyde precipitated. The operating conditions along with reaction pressure, temperature and residence time are summarized in Tables 22 and 23.

Conversion, space-time yield, and selectivity of reacted formaldehyde to end products are summarized in Table 24. During analysis, glycolic acid oligomers and other forms of glycolic acid were hydrolyzed and converted to free monomeric glycolic acid equivalents. The selectivity of conversion of formaldehyde is reported as free glycolic acid equivalents. Methanol was present as both free methanol and methyl glycolate, and was converted to free methanol and glycolic acid by the analytical method.

TABLE 22 Feed 1: Rate and Composition Ex g/min Paraformaldehyde water G1 H₂SO₄ 154 0.68 13.8 8.3 70.2 7.7 155 1.01 13.8 11.7 70.0 4.5 156 1.01 13.8 11.6 70.0 4.5 157 1.66 13.0 17.2 66.0 3.8 158 1.02 14.4 4.3 73.2 8.0 159 0.94 29.8 28.6 37.8 3.8

TABLE 23 Overall Feed Ratios and Reaction Conditions Feed Molar Ratio Temp Press Res Time Ex Paraformaldehyde water G1 H₂SO₄ Celsius psig minutes 154 1.0 1.0 2.0 0.170 170 1502 180 155 1.0 1.4 2.0 0.100 200 699 120 156 1.0 1.4 2.0 0.100 190 703 120 157 1.0 2.2 2.0 0.089 205 2603 72 158 1.0 0.5 2.0 0.170 190 1901 120 159 1.0 1.6 0.5 0.039 205 2605 120

TABLE 24 Selectivity, Conversion, and Space-Time Yield Results Molar Space-Time % F0 Selectivity Yield Ex Conv G1 A1 DG MGH MeOH gmol/l-hr 154 92 94.06 1.06 3.82 0.00 1.06 1.73 155 87 64.56 10.72 5.56 16.86 2.29 1.05 156 85 70.00 10.80 3.00 10.40 5.70 1.55 157 93 89.22 2.90 4.12 1.72 2.04 3.55 158 97 84.63 1.24 11.97 1.85 0.32 2.51 159 95 89.96 3.04 2.91 2.11 1.98 4.94 

We claim:
 1. A process for the preparation of glycolic acid, comprising (A) feeding carbon monoxide, aqueous formaldehyde, and a carboxylic acid comprising 3-6 carbon atoms to a hydrocarboxylation reaction zone comprising a solid acid catalyst to produce an effluent comprising esters of glycolic and carboxylic acids; (B) hydrolyzing said effluent to produce a hydrolyzed mixture comprising glycolic acid and said carboxylic acid; (C) recovering said carboxylic acid from said hydrolyzed mixture by extracting said hydrolyzed mixture with a hydrophobic solvent selected from at least one of the group consisting of esters having from 4 to 20 carbon atoms, ethers having from 4 to 20 carbon atoms, ketones having from 4 to 20 carbon atoms, and hydrocarbons having from 6 to 20 carbon atoms to form an aqueous raffinate phase comprising a major amount of said glycolic acid contained in said hydrolyzed mixture and an organic extract phase comprising a major amount of said carboxylic acid contained in said hydrolyzed mixture; and (D) separating said aqueous raffinate phase and said organic extract phase.
 2. The process according to claim 1, wherein said feeding of said carboxylic acid and said aqueous formaldehyde in step (A) occurs at a molar ratio of carboxylic acid:formaldehyde of from 0.5:1 to 6:1.
 3. The process according to claim 1, wherein said feeding of said carboxylic acid and said aqueous formaldehyde in step (A) occurs at a molar ratio of carboxylic acid:formaldehyde of from 0.5:1 to 4:1.
 4. The process according to claim 1, wherein said feeding of said carboxylic acid and said aqueous formaldehyde in step (A) occurs at a molar ratio of carboxylic acid:formaldehyde of from 0.5:1 to 2.5:1.
 5. The process according to claim 1, wherein said hydrolyzed mixture comprises water and said glycolic acid in a molar ratio of water:glycolic acid of from 1:1 to 15:1.
 6. The process according to claim 1, wherein said hydrolyzed mixture comprises water and said glycolic acid in a molar ratio of water:glycolic acid of from 1:1 to 8:1.
 7. The process according to claim 1, wherein said hydrolyzed mixture comprises water and said glycolic acid in a molar ratio of water:glycolic acid of from 1:1 to 6:1.
 8. The process according to claim 1, wherein said hydrophobic solvent is selected from at least one of the group consisting of ethyl acetate, n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate, s-butyl acetate, methyl benzoate, i-butyl isobutyrate, 2-ethylhexyl acetate, cyclohexyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, i-propyl propionate, i-butyl propionate, n-butyl propionate, s-butyl propionate, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ethers, methyl tertiary-butyl ether, methyl tertiary-amyl ether, methyl ethyl ketone, methyl i-butyl ketone, methyl i-propyl ketone, methyl propyl ketone, dibutyl ketone, diisobutyl ketone, isophorone, 3,3,5-trimethylcyclohexanone, cyclohexanone, 2-heptanone, methyl-iso-amyl ketone, diethyl ketone, 5-ethyl 2-nonanone, diamyl ketone, diisoamyl ketone, heptane, hexane and toluene.
 9. The process according to claim 1, wherein said carboxylic acid is selected from at least one of the group consisting of propionic acid, n-butyric acid, i-butyric acid, 2-methyl butyric acid, n-valeric acid, and i-valeric acid.
 10. The process according to claim 1, wherein said carboxylic acid comprises propionic acid.
 11. The process according to claim 1, wherein greater than 90 weight percent of said carboxylic acid is recovered in said organic extract phase and wherein greater than 90 weight percent of said glycolic acid is recovered in said aqueous raffinate phase.
 12. The process according to claim 1, wherein said extracting in step (C) occurs in a continuous counter-current extractor, wherein said raffinate phase exits the bottom of said extractor and said extract phase exits the top of said extractor, wherein said hydrophobic solvent is fed to said extractor below said hydrolyzed mixture, and wherein the feed ratio of said hydrophobic solvent to said hydrolyzed mixture ranges from 0.5:1 to 20:1 on a weight basis.
 13. The process according to claim 12, further comprising feeding a hydrophilic solvent to said extractor above said hydrolyzed mixture, wherein the feed ratio of said hydrophilic solvent to said hydrolyzed mixture ranges from 0.01:1 to 5:1 on a weight basis.
 14. The process according to claim 12, wherein said feed ratio of said hydrophobic solvent to said hydrolyzed mixture ranges from 0.5:1 to 4:1 on a weight basis.
 15. The process according to claim 1, wherein said aqueous formaldehyde comprises 35 weight percent to 85 weight percent formaldehyde, based on the total weight of said aqueous formaldehyde, the molar ratio of carbon monoxide to formaldehyde ranges from 1:1 to 10:1, and said hydrocarboxylation reaction zone is operated at a pressure of from 35 bar gauge to 200 bar gauge and a temperature of from 120° C. to 220° C.
 16. The process according to claim 1, wherein said solid acid catalyst is selected from at least one of the group consisting of sulfonic acid resins, silica-aluminate, silica-alumino-phosphates, heteropolyacids, supported heteropolyacids, sulfuric acid treated metal oxides, and phosphoric acid treated metal oxides.
 17. The process according to claim 1, further comprising (E) separating said organic extract phase into said hydrophobic solvent and said carboxylic acid, recycling said hydrophobic solvent to step (C), and recycling said carboxylic acid to step (A).
 18. The process according to claim 17, further comprising (F) reacting a first ethylene glycol with said aqueous raffinate phase while simultaneously removing water to produce an esterification effluent comprising glycolate ester oligomers and glycolic acid oligomers and an overhead stream comprising water; and (G) reacting hydrogen with said esterification effluent to produce a second ethylene glycol, separating said second ethylene glycol into a product ethylene glycol and said first ethylene glycol, and recycling said first ethylene glycol to step (F).
 19. A process for the preparation of glycolic acid, comprising (A) feeding carbon monoxide, aqueous formaldehyde, and carboxylic acid selected from at least one of the group consisting of propionic acid, n-butyric acid, i-butyric acid, 2-methyl butyric acid, n-valeric acid, and i-valeric acid to a hydrocarboxylation reactor zone comprising a solid acid catalyst to produce an effluent comprising esters of glycolic and carboxylic acids; (B) hydrolyzing said effluent to produce a hydrolyzed mixture comprising glycolic acid and said carboxylic acid; (C) recovering said carboxylic acid from said hydrolyzed mixture by extracting said hydrolyzed mixture with a hydrophobic solvent selected from at least one of the group consisting of n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate, s-butyl acetate, methyl propionate, ethyl propionate, i-propyl propionate, methyl tertiary-butyl ether, methyl i-butyl ketone, methyl i-propyl ketone, methyl propyl ketone, and toluene to form an aqueous raffinate phase comprising a major amount of said glycolic acid contained in said hydrolyzed mixture and an organic extract phase comprising a major amount of said carboxylic acid contained in said hydrolyzed mixture; and (D) separating said aqueous raffinate phase and said organic extract phase.
 20. The process according to claim 19, wherein said feeding of said carboxylic acid and said aqueous formaldehyde in step (A) occurs at a molar ratio of carboxylic acid:formaldehyde of from 0.5:1 to 4:1.
 21. The process according to claim 19, wherein said feeding of said carboxylic acid and said aqueous formaldehyde in step (A) occurs at a molar ratio of carboxylic acid:formaldehyde of from 0.5:1 to 2.5:1.
 22. The process according to claim 19, wherein said hydrolyzed mixture comprises water and said glycolic acid in a molar ratio of water:glycolic acid of from 1:1 to 8:1.
 23. The process according to claim 19, wherein said hydrolyzed mixture comprises water and said glycolic acid in a molar ratio of water:glycolic acid of from 1:1 to 6:1.
 24. The process according to claim 19, wherein said hydrophobic solvent is selected from at least one of the group consisting of n-propyl acetate, i-propyl acetate, methyl propionate, ethyl propionate, i-propyl propionate, methyl tertiary-butyl ether, and methyl i-butyl ketone.
 25. The process according to claim 19, wherein said carboxylic acid comprises propionic acid.
 26. The process according to claim 19, wherein greater than 90 weight percent of said carboxylic acid is recovered in said organic extract phase and wherein greater than 90 weight percent of said glycolic acid is recovered in said aqueous raffinate phase.
 27. The process according to claim 19, wherein said extracting in step (C) occurs in a continuous counter-current extractor, wherein said raffinate phase exits the bottom of said extractor and said extract phase exits the top of said extractor, wherein said hydrophobic solvent is fed to said extractor below said hydrolyzed mixture, and wherein the feed ratio of said hydrophobic solvent to said hydrolyzed mixture ranges from 0.5:1 to 4:1 on a weight basis.
 28. The process according to claim 27, further comprising feeding a hydrophilic solvent to said extractor above said hydrolyzed mixture, wherein the feed ratio of said hydrophilic solvent to said hydrolyzed mixture ranges from 0.01:1 to 5:1 on a weight basis, and wherein said feed ratio of said hydrophobic solvent to said hydrolyzed mixture ranges from 0.5:1 to 4:1 on a weight basis.
 29. The process according to claim 19, wherein said aqueous formaldehyde comprises 35 weight percent to 85 weight percent formaldehyde, based on the total weight of said aqueous formaldehyde, the molar ratio of carbon monoxide to formaldehyde ranges from 1:1 to 10:1, and said hydrocarboxylation reaction zone is operated at a pressure of from 35 bar gauge to 200 bar gauge and a temperature of from 120° C. to 220° C.
 30. The process according to claim 19, further comprising (E) separating said organic extract phase into said hydrophobic solvent and said carboxylic acid, recycling said hydrophobic solvent to step (C), and recycling said carboxylic acid to step (A); (F) reacting a first ethylene glycol with said aqueous raffinate phase while simultaneously removing water to produce an esterification effluent comprising glycolate ester oligomers and glycolic acid oligomers and an overhead stream comprising water; and (G) reacting hydrogen with said esterification effluent to produce a second ethylene glycol, separating said second ethylene glycol into a product ethylene glycol and said first ethylene glycol, recycling said first ethylene glycol to step (F). 